From The Times of December 14th, 1877. 
 
 " Science in the Nursery, or Children's Toys and 
 what they teach " is written, as the introduction 
 states, on the principle of drawing out from the 
 most familiar objects the t6pics of interest which 
 they 'afford. There are, it observes, many different 
 ways of looking at every object, and what any 
 given subject is to us depends mostly on the point 
 of view from which we regard it, and the sort 
 of 'eyes which are engaged in its inspection. On 
 applying this principle to the contents of a toy- shop, 
 it will be found* that the mechanism and action of 
 the simplest toys connect themselves with important 
 questions in science. This book is written on the 
 plan of drawing out the elementary lessons of general 
 knowledge which even children's toys can teach. It 
 treats in this way. of the zoe trope and some other 
 optical toys ; dolls, tumblers, and other balancing 
 toys ; flying tops, shuttlecocks, arrows, bowls, sails 
 and squirts and pumps, and cartesian divers ; spinning 
 dolis, peashooters, balls, the kaleidoscope, tops, kites, 
 bats, and hoops ; and there is added as a conclusion 
 " a glance at a soap-bubble." The style of the little 
 work is just such as a highly-educated man whom 
 his children persuaded to talk to them about their 
 toys would be likely to use in discoursing to them on 
 the objects of their amusement. We see in every 
 page how, in the hands of a man of intellect, 
 anything, however familiar, can be made interesting ; 
 some ' new light is thrown upon it, some curious 
 pieoe of historical information as to its origin ; or it 
 is made to illustrate some grand law of nature or 
 some discovery of science ; and all is enhanced by 
 grave touches ol humour. 
 
Table of "Contents. 
 
CHILDREN'S TOYS, 
 
 AND SOME ELEMENTARY LESSONS 
 LN GENERAL KNOWLEDGE 
 WHLCH THEY TEACH. 
 
 WITH ILLUSTRATIONS. 
 
 LONDON: 
 
 C. KEGAN PAUL & CO., i PATERNOSTER SQUARE. 
 
 i877. 
 
CLAY AND TAYLOR, PRINTERS 
 
 LIBRARY 
 
CONTENTS. 
 
 PAGE 
 
 INTRODUCTION ... ... ... ... 1 
 
 CHAP. 
 
 I. THE ZOETROPE AND SOME OTHER OPTICAL TOYS 5 
 
 II. DOLLS ... ... ... ... ... ... 46 
 
 III. TUMBLERS, AND OTHER BALANCING TOYS ... 53 
 
 IV. FLYING TOPS, SHUTTLECOCKS, ARROWS, BOWLS, 
 
 SAILS, ETC. ... ... ... ... ... 99 
 
 V. SQUIRTS AND PUMPS ; CARTESIAN DIVERS ... 1 35 
 
 VI. SPINNING DOLLS ... ... ... ... ... 181 
 
 VII. PEASHOOTERS ... ... ... ... ... 211 
 
 VIII. BALLS ... ... 214 
 
 IX. THE KALEIDOSCOPE ... 229 
 
 X. TOPS ... ... ... 241 
 
 XI. KITES ... ... ... ... 269 
 
 xii. bats ; hoops 277 
 
 conclusion : a glance at a soap-bubble ... 289 
 
CHILDREN'S TOYS. 
 
 INTRODUCTION". 
 
 " Sunt hsec trita quidem, Zoile, sed mea sunt." 
 
 Martial. 
 
 HE purpose with which the following pages 
 were written, and that also with which 
 they are published, should be stated, since 
 much both of the language which is used 
 and of the matter which is introduced would, without 
 explanation, appear to be inappropriate. The Author, 
 having been desired to give a lecture to a rural 
 audience, chose for his subject " Children's Toys," 
 partly because the theme in many respects promised 
 well, commending itself as dealing with pleasant and 
 familiar objects, and partly because it afforded a thread 
 on which many topics of interest might be strung. It 
 also seemed to be one upon which a busy man, having 
 no leisure beyond such moments as he could snatch 
 from an occupation followed amidst the din and dis- 
 tractions of a public place of business, might contrive 
 
 B 
 
2 
 
 children's toys. 
 
 to put together something or other ee out of his own 
 head/' as children say, which might possibly serve to 
 entertain villagers, reference to books not being, of 
 pourse, practicable under the circumstances. It was 
 thus unavoidable that the material of the proposed 
 lecture should be drawn only from such modest stores 
 of rudimentary general information as the author 
 might happen to possess. The merit, which in the 
 present case may be a doubtful one, of originality thus 
 belongs to the present essay, composed as it was under 
 such conditions as have been mentioned. If, therefore, 
 anything whatever should be found by the reader to 
 have been borrowed from elsewhere, this occurrence 
 must be due to the undetected personation of original 
 thought by an accidental and unrecognised waif of 
 memory. 
 
 The plan on which the present writer addressed 
 himself to the task imposed upon him was not such, 
 possibly, as is usually adopted, but which he desires 
 to submit to the consideration of other people who 
 may be called upon for a service like that demanded 
 from himself, since it may be found, perhaps, to be 
 not altogether a bad one. The plan in question was 
 that of collecting whatever points of instruction or 
 interest occurred to mind as being in legitimate con- 
 nection (not limiting the claim to this relationship too 
 strictly in deserving cases) with the theme to be dis- 
 cussed, and then putting these into something of 
 bodily shape, and methodical array, by a written paper 
 having the form of a lecture, but expressly intended 
 to serve no farther purpose than that of fixing the 
 several matters, and their sequence, on memory, so that 
 
children's toys. 3 
 
 they could be recalled without effort. So far from any 
 attempt being made, or desired to be made, to put 
 even a single thought or statement into any such fixed 
 terms as might be afterwards used to convey it in oral 
 delivery, it was held that as a broad general rule which 
 was applicable with exceptional force and strictness to 
 such a case as that which was in hand, the most dis- 
 astrous course which can be pursued with reference to 
 a popular lecture, (as to most addresses of all kinds,) is 
 that its exact words should be premeditated. Recited 
 language, whether the fact that it is cut and dry, and 
 not fresh, be discernible or not, may be faultless in it- 
 self, but has rarely the life and effectiveness which 
 belong to the rough and ready inspiration of the 
 moment. 
 
 It frequently happens that a petition comes from a 
 clergyman entombed, perhaps, in some remote, dank, 
 and joyless hamlet in the Fens, or immured in one of 
 the woody and secluded fastnesses of the Weald, to an 
 old College friend whose lot is cast in livelier scenes, 
 begging him, if possible, for old acquaintance' sake, to 
 come and " give an evening" at the tiny Eeading Room 
 of the Parish, and stir the stagnant atmosphere of the 
 local mind with a few fresh ideas, and the sound of an 
 unfamiliar voice. Such a request, apart from any 
 regard to the quarter whence it comes, will be in- 
 dulgently entertained in spite of personal inconveni- 
 ence by any one who knows the generosity of kind- 
 ness with which people in country districts ignore all 
 shortcomings, and accord, like true gentlefolks, a cor- 
 dial recognition to any effort honestly made, however 
 feeble and barren it may be, to lighten for them 
 
4 
 
 children's toys. 
 
 though but for a moment the leaden monotony of 
 their lives. The following pages are published in the 
 hope, which is, however, but very diffidently indulged, 
 that they may afford some aid or suggestions towards 
 a lecture on a subject of which, in good hands, much 
 might be made, and which also possesses the advantage 
 of being easily illustrated by objects which are cheap, 
 and nowhere far to seek. 
 
CHAPTER I. 
 
 HE will suppose ourselves, if you please, in a 
 toy- shop. Now pray do not credit, or, more 
 properly speaking, discredit me with such 
 impertinence as that of inviting you to be- 
 stow attention on things which, although, no doubt, 
 they belong to the children's domain, are frivolous or 
 puerile. You will remember that there are a thousand 
 different ways of looking at every object, according 
 to the particular standpoint for contemplation which 
 the spectator takes up with reference to it, and that 
 what any given subject is to us depends mostly on 
 the point of view from which we regard it, and the 
 sort of eyes which are engaged in its inspection. This 
 reflection has not the merit of novelty, since it is 
 borrowed from Lucretius, a poet and philosopher who 
 lived about 2000 years ago. 
 
 Now on applying this principle to the survey of the 
 contents of a toyshop, it will be found that the mechan- 
 ism and action of the simplest toys connects itself with 
 important questions in science. Before we part com- 
 pany you will have plenty of opportunities forjudging 
 whether this statement is exaggerated or not. Some 
 
6 
 
 children's toys. 
 
 years ago a clever book was written and published by 
 some Cambridge men, partly containing translations 
 into Greek and Latin verse of old English nursery 
 rhymes. My plan for this evening is to attempt to do 
 something which may be described as the converse of 
 the task to which the authors of the " Arundines Cami " 
 addressed themselves. They transferred the poetry 
 of the nursery into language in which it could not be 
 understood except by classical scholars. Now toys 
 speak a language of their own which is Greek to the 
 ignorant, and requires construing into simple English, 
 but which, when it is thus rendered intelligible, is 
 found to be rich in instruction, and to teem with sug- 
 gestiveness. 
 
 A complete account of what toys are, how they are 
 born into the world from the manufacturer's hands, 
 and what is the nature and significance of all the 
 various actions which they are capable of exhibiting, 
 could not be given within the fraction of an evening 
 which is allotted to a lecture. The discussion would 
 fill a series, not merely of English winter evenings, 
 but of nights as protracted as those which occur in the 
 moon, where, as you probably know, each alternate spell 
 of light and darkness lasts a fortnight. An Arctic 
 night, indeed, of several months' duration might not 
 allow us to get through the subject. We will therefore 
 confine curselves to a glance at toys in some few of 
 their scientific aspects only, since these are of much 
 more real and substantial interest than descriptions of 
 the processes of manufacture. Themes of this latter 
 kind are better adapted for supplying what is called 
 ' ' padding *' to popular magazines, that is to say, for 
 
children's toys. 
 
 7 
 
 furnishing forth the literary matter of a mediocre, or 
 neutral, quality which is wanted for intermixing with 
 the better articles which are alone worth something, 
 so as to swell the bulk of the whole publication to a 
 size which may appear to justify its price. 
 
 Which toy shall we look at first ? Suppose we pro- 
 ceed on the established principle of " seniores priores^, 
 that is to say, give precedence to age, and begin with 
 the zoetrope. Our selection will be well justified, for 
 the zoetrope, in its original and simplest form, is 
 probably the oldest toy which is known. Some of you 
 may feel an impulse to interrupt me here, and say that 
 the zoetrope is one of the very youngest, instead of the 
 
 oldest, of toys, for that you recollect its being intro- 
 duced to the world for the first time, as a novelty, only 
 a few years ago. It is quite true that it was then 
 brought out in a fresh form, as a new thing, but it 
 had been already well known in other shapes, and 
 
8 
 
 childeen's toys. 
 
 under other names, for any number of years. When I 
 was a boy it was the " phenakistikope." The phena- 
 kistikope still survives at the Polytechnic in Regent 
 Street, where it is called the " thaumatrope." There 
 .is, as we know, " nothing new under the sun," and 
 toys, like fashions, come out again and again in resus- 
 citated existences. The zoetrope is thus only an old 
 friend with a new face. 
 
 You must understand me, if you please, to have 
 been speaking of the principle on which the toy is 
 founded, and which may be explained iu the following 
 manner. Suppose you have a ball attached to the 
 end of a string, and that you whirl it round in the 
 air, what is the appearance which is presented ? The 
 ball appears to form a ring. Or suppose that you take 
 a stick with a red-hot end, and brandish it about, you 
 can make with it long lines and curves of light of any 
 pattern you please. Boys came into the world before 
 toys, and you may be sure that displays of home-made 
 fireworks of this humble order afforded a favourite pas- 
 time long before kites and rocking-horses were invented. 
 
 Now how is it that the semblance of a ring is 
 created by a whirling ball, and a line of light by a 
 single bright point when in rapid motion ? The illu- 
 sions in question are brought about by what is called 
 the " persistence of vision." A real understanding of 
 what is called the persistence of vision supplies a mas- 
 ter key which will unlock the secret of all sorts of toys, 
 and of all sorts of other things besides, so that it is 
 desirable to make sure of its acquisition by taking 
 with due care and patience the steps which are requi- 
 site for the purpose. 
 
children's toys. 
 
 9 
 
 Now consider, if you please, the box which you 
 have here before you to be a room, and imagine a 
 bright sun, represented by this lamp, to be shining 
 outside the window. The shutters are supposed to be 
 
 shut so that the room is dark. Bore at any spot in 
 the side of the box where the shutters may be taken 
 to be, a hole through which some rays of light can 
 pass, and conceive these to fall, as they would naturally 
 do, unless the sun were very high, on the wall opposite 
 to the window. And lastly, fancy that a sheet, repre- 
 sented by this piece of paper, is hung up on that wall, 
 just as if a magic lantern entertainment were about to 
 take place. 
 
 Now here you have an exact counterpart, only 
 on a larger scale, of an apparatus of which every 
 person present has two examples in his or her own 
 person — -that is to say of the arrangements constituting 
 the human eye. The hole in the shutters answers 
 to the small black spot called the iris in the middle of 
 the pupil through which light, bringing in itself the 
 pictures of external objects, enters the eye. The sheet 
 corresponds with a structure of very delicate and 
 sensitive material, a sort of little curtain of exquisitely 
 
10 
 
 CHILDBEDS TOYS. 
 
 fine texture, which is stretched at the back of the eye, 
 and on which the images of objects towards which the 
 sight is directed fall. This membrane is called the 
 " retina So that if you could look through the hole 
 in each pupil of your friend's eyes while you are talking 
 to him, you would behold a vivid, truthful, and perfect 
 miniature portrait of yourself such as the hand of man 
 would fail to accomplish, painted in duplicate on his 
 two retinas, like images thrown from magic lanterns 
 upon sheets, or the brilliant little scenes displayed by 
 a camera obscura. The pictures would be, in truth 
 and fact, coloured photographs. 
 
 We must not get upon the general subject of eyes 
 just now because we have to do this evening with but 
 one point only connected with them, and which, too, 
 is solely concerned with the behaviour of the retina; 
 but it may not be out of place to caution you against 
 taking in too broad a sense what has been said of the 
 dark room, the hole in the shutter, and the sheet, as 
 collectively representing in a very general and rough 
 manner the whole machinery of sight. Does any one 
 suppose that we see with our eyes ? We certainly do 
 not. Our eyes (and by eyes I here mean the round 
 balls which human beings and most other animals 
 carry on the two sides of the bridges of their noses, or 
 of their beaks, as the case may be,) correspond with 
 the shutters, and are each pierced, like them, by a hole ; 
 while the retina plays the part of the sheet. Eyes, 
 therefore, in real truth and fact, no more see than the 
 perforated shutters and the sheet can be said to do so. 
 What really does see is the brain. For from the back 
 of each eye a nerve, called the optic nerve, goes up to 
 
children's toys. 
 
 11 
 
 the brain and conveys to that organ in some inscrut- 
 able way impressions of the pictures thrown upon the 
 retina. It is the brain, therefore, which sees, but how 
 does it do so ? Here we come on that mysterious 
 borderland where matter and spirit meet. To the 
 inquiry therefore " how do we see ? " there is, in the 
 present state of human knowledge, and probably will 
 be for an indefinite time to come, but one reply, which 
 may be given in Lord Dundreary's words : " It's a thing 
 which no fellow can understand." Not sight alone, 
 but all our senses, of course, present a similar enigma, 
 which in every case is equally insoluble. 
 
 To return from these perplexing speculations to the 
 One simple property of the eye with which the principle 
 of the zoetrope is concerned, which is this. When a 
 picture of any kind is thrown upon a sheet, it dis- 
 appears the very instant that the light by which it is 
 generated is turned aside or intercepted by a screen 
 brought across its path, or as soon, of course, as the 
 source whence it emanates is withdrawn. But when 
 the miniature of an object is thrown upon the retina of 
 an eye, then it does not vanish at the very same 
 moment that the rays by which it has been painted are 
 diverted or fail, but some little time, very short no 
 doubt, but none the less a real and definite space of it, 
 which is quite appreciable and can be measured, elapses 
 before the impression which has been produced fades 
 away. 
 
 The precise limit of duration of the survival of 
 the image after the origin of the light which is ne- 
 cessary to sustain its existence has discontinued its 
 supplies, or been shut off, depends on particular cir- 
 
12 
 
 children's toys. 
 
 cumstances, such, as, for example, the degree of force 
 with which the impression has been made, which is 
 greater, of course, in the case of a bright or clear 
 object, and less in that of a dark or dim one, and the 
 longer or shorter extent of time through which the 
 process of engraving (for that, as will be explained 
 presently, is the term which is the most accurately 
 appropriate) has lasted. Each colour too, apart from 
 its degree of brilliancy, whatever that may happen to 
 be, has its own individual and characteristic rate of 
 scoring its mark on the retina, red being the tardiest 
 in such workmanship, and blue the most expeditious. 
 
 Moreover, an object or scene may be within range 
 of view for too limited a period, or may be too faint, or 
 too small, or through some combination of these or 
 other incidents may exercise so transient or weak an 
 action on the retina as not to make itself visible at all. 
 
 We are not, for example, conscious of the frequent 
 intervals of pitch darkness which occur as often as we 
 wink. A cannonball shot across your face would be 
 too rapid in its passage to be visible. On the other 
 hand, under certain particular conditions which may 
 be arranged by an experimenter, a visual impression 
 may be caused to last much longer than such images 
 under ordinary circumstances do. But we will omit 
 exceptional cases, and deal with such experiences 
 only as are common and familiar. 
 
 Suppose, then, that a spark of fire which has 
 depicted itself on the retina, is moved to a spot close 
 alongside of that where it has been seen ; and suppose 
 that immediately afterwards it is again shifted to an 
 adjoining position j and imagine this process to be 
 
children's toys. 
 
 13 
 
 repeated a great many times, then the idea which the 
 brain will acquire of what has been presented to view 
 will be that of a continuous line of fire, because the 
 earlier impressions made upon the eye will not have 
 had time to die away before the later ones join on to 
 them. A streak of lightning is merely an electrical 
 spark travelling so rapidly that, as far as perception by 
 human sight is concerned, it is at every point of its 
 whole journey at the same time, thus qualifying in a 
 certain sense the truth of the old saying that nothing 
 can be in two places at once. 
 
 An explanation of this phenomenon which attends 
 the faculty of seeing, and which is called the " per- 
 sistence of vision/' has been propounded by the theory, 
 which in all probability gives a true account of the 
 matter, that an actual scar, that is to say a local altera- 
 tion of structure in the organism of the eye, is induced 
 by the action of light at the spot upon which it falls, 
 and where it brands, as it may almost literally be said 
 to do, its mark. As in the case of other scars, it takes 
 some time for the membrane which has been thus af- 
 fected to re-establish the original arrangement of its 
 particles, and thus obliterate the traces of the disloca- 
 tion produced among them through the blow struck 
 by light in its impact on the retina. 
 
 It should perhaps be stated that the blow thus in- 
 flicted on the retina is not a single one, but a sustained 
 hailstorm, so to speak, of infinitely small strokes de- 
 livered in rapid succession. A ray of light is, in 
 fact, mechanically speaking, a line of waves following 
 one another in a file which issues continuously from 
 the source of illumination. Light is thus a system of 
 
n 
 
 children's toys. 
 
 undulations, and the several rays of which it consists 
 (for, as you will hear presently, it is of a composite 
 nature) are each of them, tiny, but energetic, ripples. 
 The size and the rapidity of motion of the wavelets 
 which go to form these ripples varies with each colour. 
 They can be measured and counted in each case, but 
 it would not be relevant to our present purposes to 
 describe the contrivances by which these appraisements 
 are accomplished. 
 
 It may be mentioned that the continued present- 
 ment of objects to view beyond the moment at which 
 they ought as it would seem, in the natural order of 
 things, to disappear, is a phenomenon which is gener- 
 ated by other causes besides that of the persistence of 
 vision. "Refraction " and "phosphorescence/' subjects 
 which we cannot now discuss, produce a like effect by 
 means which may be just glanced at, and then dis- 
 missed. For example, it constantly happens through 
 refraction that a body which has been shut off from 
 direct view by an opaque shield set up between it and 
 the spectator, as the setting sun is by the revolving 
 Earth, continues to be seen round the corner, as it 
 were, of the interposed screen, through the bending of 
 the rays, as they pass from the object in question to the 
 eye of the spectator, through some medium which is 
 capable of diverting them from their naturally straight 
 course. Phosphorescence is a property which all objects 
 seem to possess in some slight degree, which is infin- 
 itely faint in most instances, but more pronounced in 
 others, (as, notably, in the case of a petal of red gera- 
 nium,) of continuing, after the light by which they have 
 been illuminated is quenched or fails, to give out rays 
 
childeen's toys. 
 
 15 
 
 of the same kind as those reflected by them up to the 
 moment of that withdrawal. 
 
 Now let me turn abruptly to a different matter, but 
 one which will be found to be quite apropos to the 
 zoetrope. Suppose that you were asked, " What is the 
 colour of things in general ? " you would probably 
 reply, " That is a question which it would take a life- 
 time to answer. Flowers exhibit an infinity of colours, 
 and sometimes even a single object, such as a harlequin's 
 coat, displays a considerable variety. Specify, there- 
 fore," you would say, " some one particular object as 
 the subject of your inquiry, and we will tell you what 
 its colour is." 
 
 I will do as you may be supposed to desire, and 
 being at liberty to select anything which the world 
 contains, will take for choice w T hat is accepted as the 
 highest ornament of the universe, — a lady's cheek. 
 What is its colour ? You will probably say, " A good 
 specimen is of a delicate pearly white and pink." My 
 rejoinder would be, " Yes, no doubt, that is the 
 appearance which it presents when seen in Society, 
 but what was meant to be asked was this (and please 
 to observe the precise terms of the inquiry) — What 
 is the original and native hue of a fair-complexioned 
 young lady's cheek independent of any tints which it 
 may borrow from the powder box or the rouge pot, or 
 which it may steal from any foreign source whatever ? " 
 The answer to this question is " black as ink." Some 
 young lady may here look aggrieved and incredulous, 
 and exclaim, " You don't mean to tell me that my face, 
 except for colours which are imparted to it by some- 
 thing or other which is no part of itself, or of myself, 
 
16 
 
 children's toys. 
 
 is like that of a negress ? " My rejoinder would have 
 to be, c< Pardon me, but the absolute requirements 
 of truth forbid me to recede from the assertion 
 which, however unacceptable to you, is one which it 
 will be impossible to confute or qualify, that your face, 
 apart from certain cosmetics with which Nature em- 
 bellishes it, is jet black." 
 
 But to speak quite seriously, it is a truth which is 
 now pretty well known to most people, that nothing in 
 the world has any colour but light. Light, and light 
 alone, supplies all the various hues w T hich are known to 
 us. When we find that a rose is pink, or a cabbage 
 green, the real fact is that the texture of a rose is so 
 constituted as to be capable of reflecting pink rays only, 
 and that of a cabbage leaf green ones alone, both colours 
 being supplied exclusively by light, without any con- 
 tribution whatever from the plant itself, in either case. 
 Neither rose nor cabbage is a source of colour in any 
 larger sense than a looking-glass is the birthplace or 
 origin of the faces which it mirrors. And since we 
 only see any object, whatever it may be, by the rays 
 which come from it to our eyes, the visual impression 
 which we get in contemplating a rose is a pink one, and 
 the image which we derive from the sight of a cabbage is 
 of a green complexion. 
 
 The gorgeous hues with which chemists' bottles are 
 resplendent are not, it is true, always and altogether re- 
 flected from the fluids inside those bottles, but still they 
 are not a whit less than in the case of a rose or a cabbage 
 extracted wholly and solely from light. The liquid in 
 each bottle when it is seen by a lamp behind it acts as 
 a sort of strainer, allowing the rays of some one particu- 
 lar colour only to traverse its substance. If the rays 
 
children's toys. 
 
 17 
 
 which thus obtain free passage are blue, we see the fluid 
 as blue ; if they are yellow the fluid is to our perceptions 
 yellow, and so on with every colour. In the case of 
 other substances, the particular rays which are dis- 
 patched from them to our eyes are not always filtered 
 from the general stock which light contains in quite so 
 simple a manner as that which has been described, but 
 it is still always true, without any modification what- 
 ever, that colour is derived exclusively from the single 
 source which has been mentioned. It has no inde- 
 pendent existence of its own, but is invariably an 
 extract from light, although the latter, until the 
 usual association of its component hues is by some 
 means severed, possesses no discernible colour of any 
 kind. 
 
 Several questions might here be reasonably asked 
 by those among you who are not familiar with these 
 matters, or who have never thoroughly realised them 
 in imagination, such, for example, as the following. If 
 light is colourless until a portion of its rays is reflected 
 from some opaque object such as a brick, or until it 
 has made its way, with a loss of some of its elements, 
 through some more or less transparent substance such 
 as glass or jelly, why does the sun sometimes look red, 
 as it is his custom to do in a fog ? For he does not, 
 like the moon, reflect rays, being himself the actual 
 source of them, nor, obviously, is his light transmitted 
 through his person to us from some spot or other in 
 the heavens behind him, as if he were but the trans- 
 lucent face of an illuminated clock. The reason that 
 his light is red under the condition of things which 
 has been referred to is that in a particular state of the 
 atmosphere the fog acts the part of a sort of colander, 
 
 c , 
 
18 
 
 children's toys. 
 
 and arrests all but the crimson rays, so that these alone 
 succeed In reaching the Earth. 
 
 Again, the question might be asked why the sky is 
 blue ; for it seems difficult to perceive how any of the 
 processes which have been hitherto described can be 
 applicable to this case. The answer is that skyblue is 
 the offspring, through reflection, of colourless light, but 
 that it is generated in a manner which is far too com- 
 plicated to be susceptible of convenient explanation 
 here. The blue, however, comes wholly and solely from 
 light. The atmosphere until, and only so long as, it is 
 steeped in a blue extract of sunbeams is as black as 
 night. As seen from the top of high mountains where 
 the conditions by which the blue is evoked are sometimes 
 wanting, the sky not unfrequently appears spread over 
 the earth like a sable pall, presenting a weird aspect. 
 An exemplification of the mechanical process from 
 which the asthereal dye ensues may readily be pre- 
 sented, for by means of a common and simple little 
 instrument, the polarising apparatus from a microscope, 
 a richer and more glorious blue may be distilled from 
 even a very small quantity of apparently colourless 
 light than was ever displayed by an Italian sky. 
 
 Up to this point I have spoken only of the state 
 of things in which some particular rays of a beam of 
 light are disengaged from the bundle to which they 
 belong by the object upon which they fall, and are trans- 
 mitted, apart from their former companions, to our sight. 
 There are two other contingencies which may happen to 
 light. It may strike something which may have the 
 property of forwarding it to our eyes in its unchanged 
 integrity, or it may encounter one of the objects which 
 
children's toys. 
 
 19 
 
 have the faculty of swallowing up and entombing it 
 altogether, so that none of it is reflected. In the first 
 case, that, namely, in which the whole of the light is 
 reflected, the object whence it rebounds is white, and 
 where it is totally absorbed, the surface into which it 
 plunges is black. 
 
 The word "absorbed" has been used to signify the 
 occurrence which takes place when rays of light falling 
 on any surface disappear there, engulfed, as it were, 
 and thus lost to sight. The term has been adopted as 
 being that which is in common use, and which founds 
 a claim to employment on " possession/' which " is nine 
 points of the law," of a place in all the text-books and 
 treatises, whether elementary or advanced, which have 
 been written upon the subject of light. By the rule of 
 "Hobson's choice," therefore, it is forced upon our ac- 
 ceptance. It will serve its purpose well enough, pro- 
 vided that it is only taken to mean as much as this, and 
 no more, namely, that rays which are said to be " ab- 
 sorbed " at any particular spot thereupon cease, as far 
 as our calculations and perceptions are concerned, to 
 have existence. The term must not be permitted to sug- 
 gest the notion that the spot in question sucks in the 
 rays by some species of action of its own, or that it is 
 in any respect otherwise than completely passive with 
 reference to them. 
 
 It may perhaps be as well, for the sake of preclud- 
 ing misunderstanding, to qualify, by a limitation which 
 is almost self-evident, the statement made a moment or 
 two ago in unreserved and general terms that an object 
 which reflects all colours is white. It is only white when 
 it gets all colours to reflect, because it cannot transmit 
 
20 
 
 childken's toys. 
 
 to the eye any hues with which it is not furnished for this 
 purpose. It has no domestic factory of home-made rays 
 whence any necessary ingredients of white light which 
 may happen to be deficient can be supplied. A sheet 
 of letter paper will be gray, yellow, green, or of any 
 other colour which may happen to fall upon it ; and in 
 the dark it will not merely seem to be, but will, in 
 actual reality, be black. The total absence of reflection 
 comes, in its result, to the same thing whether it be 
 due to want of light, or to the absorbent character of 
 the surface on which rays fall, and is blackness in the 
 one case just as much as in the other. Be it, therefore, 
 well remembered that colour is simply the result and 
 creature of a process, namely, that of reflection, and 
 that it can thus last so long only as this is actually 
 sustained, being altogether dependent upon it from 
 instant to instant for its existence. 
 
 Colour, moreover, must thus necessarily vary with 
 every circumstance by which the source of its being is, 
 however transiently, affected. We call a sheet of paper 
 white because it is convenient to speak of familiar objects 
 as being of some particular distinctive hue which is con- 
 ventionally attributed to them as their permanent pro- 
 perty, and we assign to each the name of the tint which it 
 wears under ordinary circumstances, just as it is said of 
 a person usually ruddy that he or she has a florid com- 
 plexion though the description may altogether fail to be 
 applicable in moments of sea sickness or alarm. But 
 no fixed colour is an integral part of the constitution 
 and essential personality of any object, a whit more 
 than the fortuitous disposition of clouds which may 
 happen to prevail at this moment is a necessary feature 
 
children's toys. 
 
 21 
 
 of the face of the sky, or our garments by day or 
 night of ourselves. 
 
 What has been said as to colour being altogether 
 the offspring of reflection is proved, when you come to 
 think of it, by the fact that a highly polished surface, 
 like that of a looking-glass, presents to the eye the 
 objects which it mirrors clothed in the hues which they 
 respectively wear at the moment, without the addition 
 or the disclosure of any tint of its own. It might be 
 added here, but this is a matter upon which we cannot 
 now enter, that colours have not even so much existence 
 as we have attributed to them, for that they reside in 
 truth and fact in our perceptions, only, and have no 
 substantive being of their own : in short, that they are 
 altogether " subjective," as it is called, and not " ob- 
 jective." 
 
 You now discern the grounds on which it was stated 
 that a feminine cheek, except for the colours which it 
 obtains from sources extraneous to itself, is black. If 
 it ceased to reflect, or, in other words, to borrow the 
 whole of its tints from light, it would simply be of a 
 jet-black. " Jet-black," indeed, would be too favour- 
 able a description of it. For jet, like other coal, has a 
 gleaminess, or whatever it may be called, of its own, 
 arising -from a certain sort and degree of reflection 
 which takes place from its hard and polished surface, 
 and which imparts to it the brilliancy which renders it 
 suitable for ornaments. An object which did not reflect 
 at all would be of a deep, dull, and repulsive black, 
 like an old hearse with all the nap worn from its cloth, 
 and the varnish from its panels. A black silk hat re- 
 flects a little, in the same manner as jet, which relieves 
 
22 
 
 children's toys. 
 
 the general darkness of its effect. A felt hat of the 
 same colour appropriates, without making any corre- 
 sponding return, nearly all the light which reaches it, 
 and it has consequently a more heavy and dead appear- 
 ance. 
 
 The account which has been given of the origin of 
 ladies' and other 'people's complexions holds good for 
 all circumstances and times, and in every detail. If 
 the tip of a human nose gets blue with cold on a frosty 
 day, or if the proprietor of that nose, on lapsing into 
 the plight of a desolate old bachelor, or old maid, is 
 led to seek comfort in the brandy bottle, and there- 
 upon the feature which has been mentioned comes by 
 degrees to a fiery red, like a wild poppy, both the phe- 
 nomena of colouring which have been specified are due 
 to changes in the circulation of the blood at the spot in 
 question, which influence the reflecting properties of 
 the skin at that particular point. If, at this moment, 
 we were to put out the candles, and play snap-dragon 
 with raisins and lighted brandy, the most rosy com- 
 plexion in the room would become, as you know, as 
 slaty and cadaverous as that of a ghost with a sick- 
 headache, because the light which comes from the flame 
 of burning brandy supplies no pink flesh-tints for the 
 human skin to reflect. 
 
 The old trick which books of what is called " par- 
 lour magic" describe of robbing a picture of all its 
 colours and thus causing it to appear to be a print, is 
 accomplished by illuminating it by the flame of salt, 
 which furnishes nothing but yellow light, so that the 
 surfaces of the various pigments on the canvas cannot, 
 severally, obtain the particular rays which alone it is in 
 
children's toys. 
 
 23 
 
 their nature, and within their capacity, to reflect. A 
 red geranium, if it were to be seen by the light of a 
 snap-dragon, would not only appear to be, but would 
 be, in the strict and proper meaning of correct language, 
 really yellow, for the time being, although it would still 
 be right to call it by the name under which it is usually 
 known, as indicating the particular species of plant 
 which it is, and correctly describing the decided charac- 
 teristic by which its flowers, under ordinary circum- 
 stances, are marked. 
 
 But how do we know that light, which, to all ap- 
 pearance, is wholly devoid of any colour, contains 
 within itself, literally speaking, all the hues of the rain- 
 bow ? Sir Isaac Newton was the first person to point 
 out that this is so, and he showed how to prove it. 
 Can we, then, take a beam of light to pieces, as we 
 might a piece of coloured mosaic, or a child's dissect- 
 ing map, and display the various ingredients which 
 enter into its composition ? Nothing is easier. We 
 can, by a simple method, break it up, and show it in all 
 its colours at once, which, when mixed on Nature's 
 palette, supply every hue which we see about us, or 
 which is anywhere to be found. By adopting a pro- 
 cess of another kind we can display these colours, and 
 the diversified combinations which they are capable of 
 forming with one another, in an absolutely endless 
 series. Anybody who works with a microscope has 
 often to dissect light in both these ways, but far more 
 frequently in the latter, as a necessary part of his re- 
 gular business. 
 
 Here is a common toy, claiming our notice in that 
 character, and which is, as you see, a mere plain three- 
 
24 
 
 children's toys. 
 
 sided piece of glass, something like a wedge, or a row of 
 wedges joined at their sides. It is called a " prism. " 
 
 3k 
 
 Green,. 
 
 This plaything, simple as it is, is a most effective in- 
 strument for dissecting light, and is a counterpart of 
 the identical tool which Newton used for the purpose. 
 Any one can repeat in an ordinary room, and with great 
 ease, the interesting and beautiful experiment by which 
 Newton's grand discovery as to the compound nature of 
 li^ht was reached. Such a prism as this forms the whole 
 apparatus which is required, and costs about sixpence, 
 but it is not necessary to spend even a penny, for it is 
 very easy to borrow (or even to steal, for so good a 
 purpose, would be an act of very mitigated tur- 
 pitude) a three-sided glass drop from a chan- 
 delier, or from one of the common lustres 
 which are to be found on a drawing-room 
 chimney-piece. Such a drop will be a toler- 
 ably good prism, and will behave as such ; and 
 the most elementary book on Science, or in- 
 deed many of the books on amusements for 
 children, such as " The Boy's Own Book," 
 will be found to give full directions as to how 
 the instrument is to be adjusted for the performance 
 of its duties. 
 
childeen's toys. 
 
 25 
 
 It is not expedient to show you the process here, and 
 now, in actual operation, because it could not be satis- 
 factorily displayed to a numerous body of spectators, 
 unless it were done on a large scale, and with a pro- 
 fusion of light, so as to exhibit the colours with due 
 brilliancy. But to accomplish this it would be neces- 
 sary to darken the room, which would be inconvenient, 
 and take time. Besides which, whenever it next hap- 
 pens that the sun shines through a shower of rain, na- 
 ture will supply an admirable working diagram illus- 
 trative of what has been said, in the shape of a rainbow. 
 The falling drops will under such circumstances have by 
 their combined action the effect of a prism, and will 
 unravel the strands, as they may be called, of white 
 light which come from the sun into the separate skeins 
 of coloured rays from which they are woven. 
 
 Do not make the mistake of imagining that when a 
 beam of light which is apparently pale is caused to pass 
 through a prism, and reappears on the other side in a 
 glorified form as a brilliant array of hues, the glass adds 
 anything of its own in the way of colour. One toy illus- 
 trates another, and the present is a favourable oppor- 
 tunity for noticing a common and favourite old play- 
 thing, to wit, a burning-glass, because this latter will 
 show that there is not the slightest ground for fancying 
 that the prism has necessarily anything to do with the 
 colours in the sense of being itself the parent of any of 
 them . 
 
 Here is a burning-glass. You recognise it by its 
 familiar shape, which is that of a circular disc, fat in 
 the middle and thin round the edge, like a solid wheel 
 with a very thick nave. You know that when you so 
 
26 
 
 childeen's toys. 
 
 hold this glass as to receive the warm rays of the sun 
 on one of its faces they meet in a bright point at a cer- 
 tain distance on the other side. The action of the glass 
 
 upon the rays is to make them converge, that is to say 
 to slope towards one another, till at last they all as- 
 semble at the same spot. And you must have found 
 that if your finger, or anything else, be placed at the 
 brilliant speck where the rays meet, it will be burnt. 
 The point in question is, as you know, called the focus, 
 and you will discern the propriety of this name for it 
 when you a learn that " focus 3> is the Latin for " fire- 
 place/' 
 
 Any substance, or combination of substances, which 
 possesses the faculty of permitting the free passage of 
 the sun's rays, and of so influencing the directions of 
 their courses as to cause them to meet at a focus, will 
 act with more or less complete effect as a burning-glass. 
 A decanter of water was one day standing on my study 
 table when the sun, although the month was October, 
 was shining into the room rather warmly. The bottle, 
 when full of clear water, formed, in effect, a solid and 
 transparent globe. It happened also to be precisely 
 
children's toys. 
 
 27 
 
 of the right construction to act well as a burning-glass, 
 since its surface was quite plain and smooth so that it 
 did not scatter irregularly the rays of light or heat 
 passing through it as it would have done if it had 
 been moulded or tattooed with a pattern, as most de- 
 canters are. The sun's rays, falling on it as they did 
 on the occasion in question, were brought by the globe 
 of water, as though by a burning-glass, to a focus, and 
 this happening to come precisely at the surface of the 
 table-cloth, burnt a hole there. 
 
 A clear piece of ice, if cut to the form of a burning- 
 glass, would comport itself as such, and you might set 
 on fire anything capable of burning by rays collected 
 and brought to a focus by its means. The experiment 
 has often been shown. You are not likely to imagine 
 that the ice would add much heat of its own to that of 
 the rays passing through it. Nor can the bottle of 
 cold water which was mentioned just now, have con- 
 tributed anything on its own account to the fire which 
 scorched the table-cloth. Similarly, the action of a prism 
 is to alter, in different degrees, the courses of the several 
 rays which pass through it, and which constitute, as 
 long as they are united, colourless light. It causes 
 each of them to part company from the rest, and to 
 disclose itself in its own separate individuality as a 
 streak of some particular hue standing confessed as 
 though at the touch of IthuriePs spear, but it supplies 
 no new tints of its own, nor does it to the slightest 
 extent intensify those which it thus compels to reveal 
 themselves. 
 
 Having dealt with a ray of light after the fashion 
 with which paupers in workhouses have to treat pieces 
 
28 
 
 children's toys. 
 
 of old rope by picking them to pieces for oakum, can 
 we put it together again ? Readily. One method of 
 so doing is by arranging a second prism in such a 
 situation and attitude as that the rays which have been 
 divorced by the first one shall be remarried, that is to 
 say, again blended, by this other. But there is a plan 
 whereby the rays may be, in effect, reunited, which is 
 founded on a principle of an altogether different kind. 
 It forms the point towards which I have been leading 
 you for some time past, and which I wished you to reach 
 fully equipped with preliminary information so as to 
 understand it fully, since it exhibits the principle of 
 the zoetrope in a very clear and interesting manner. 
 
 You were told just now that when an object reflects 
 all the colours of the rainbow it appears to our eyes as 
 white. You also learnt that when we see anything 
 which is afterwards withdrawn from sight, it still, to our 
 perceptions, remains for a very short time at the place 
 where we originally beheld it, because the visual impres- 
 sion made by it upon the retina of the eye takes some 
 little time (which averages about one-eighth of a 
 second) to fade away. From these circumstances it 
 follows that if we could bring all the separate colours of 
 which a ray of light is composed, in sufficiently rapid 
 succession, to one spot, we should, in effect, see them 
 all together, and thus get a perception of white as 
 the general result. This " chromatic," that is to say, 
 variegated, disc, forms a device for accomplishing this 
 experiment, and it will prove what has been told you 
 about the composition of white light, and the persist- 
 ence of vision, to be true. 
 
 We have here, as you observe, all the colours of the 
 
children's toys. 29 
 
 rainbow disposed in their proper order in triangular, or 
 wedge-shaped, areas, or what are called sectors of a 
 
 circle, following one another in the same sequence 
 which Nature herself observes when arranging them in 
 the sky. They are repeated in similar groups all round 
 the disc. Now consider any point you please upon the 
 disc, such, for example, as this one at the top. The 
 colour which happens to be there at this moment is 
 orange. If the disc be spun very rapidly, all the other 
 colours will come in their turn, in quick succession, to 
 the same point, and before the impression which any one 
 of them makes upon the eye of the spectator has faded 
 away, each of the others will have scored its own mark 
 at the same spot. The spectator, therefore, will in the 
 result see at this point all colours, that is to say, white. 
 What is true for any one point in the disc is, of course, 
 by a like process of reasoning, no less true for any 
 and all others which might be taken on the same 
 surface, so that the whole presentment to the eye is 
 white. 
 
30 
 
 children's toys. 
 
 The disc might just as well, as far as the pur- 
 pose for which it has been used is concerned, have 
 been painted with fewer stripes of colour than are actu- 
 ally employed ; with any number, in fact, not less than 
 two. For since all the colours of the rainbow, taken 
 together, make white, it is plain that if you combine, 
 say, half of them in one mixture, and the other half 
 in a second, in the proper proportions, of course, in each 
 case these two groups, when united, will assume the 
 hue of which they are the ingredients, whenever they 
 are amalgamated to the eye by sufficiently rapid motion. 
 Any two colours, thus, by their combination, producing 
 white, are said to be " complementary 9} to one another. 
 
 That the blending of the colours is really and alto- 
 gether due to the cause which has been stated is proved 
 by the fact that if the disc, when spun as before, be made 
 visible for so short a time only as that no motion which 
 is sufficiently large to become appreciable by our 
 senses takes place within it, the colours all appear 
 separate, just as if the whole apparatus were at rest. 
 To all intents and purposes it is so, as far as the 
 spectator is concerned. If the disc be illumined 
 brightly, but only for some infinitesimal portion of an 
 instant, as, for example, by means of the electric spark, 
 which gives a fk,sh of a duration of less than the four- 
 thousandth part of a second, no motion, nor any con- 
 sequence of motion in the shape of fusion of hues, is 
 perceptible. Similarly, if a man galloping at night on 
 a fleet horse were to be revealed, for a moment only, 
 by a flash of lightning, he would appear to be stand- 
 ing stock still. 
 
 Any one desiring to pursue this subject further 
 
children's toys. 
 
 31 
 
 should make inquiries as to certain cogged wheels 
 devised by Faraday illustrating the effects of persist- 
 ence of vision, and exhibiting a multiplicity of very 
 curious optical phenomena. The only apparatus re- 
 quired will be such as anybody can make, and it will 
 cost absolutely nothing. 
 
 Here is another toy depending upon and illustrating 
 that property of our eyesight with which we are now so 
 familiar under the title of persistence of vision, and 
 since the contrivance which is before us seems to 
 occupy a position as a sort of halfway house between 
 the chromatic disc and the zoetrope, it has a valid claim 
 to be noticed at this moment. On one side of this card, 
 as you see, is a horse, and on the other side a rider. 
 By making the card spin rapidly, so as to present its 
 two faces alternately in quick succession, the figure on 
 one side combines in its effect to the eye with that on 
 the other, and the general result is a complete picture 
 of horse and rider. 
 
 This toy is capable of a very practical application to 
 the serious exigencies of real life. For conceive an in- 
 
32 
 
 childeen's toys. 
 
 cident of the following kind. Such things have oc- 
 curred, are daily occurring, and will continue to occur 
 till the end of time, so that you will not be called upon 
 to exert any violent spasm of imagination in picturing 
 to yourselves the scene which is to be conceived. 
 Pretty young lady, unmarried, but with no intention to 
 remain so. Eligible young gentleman, a warm admirer 
 of the young lady, but perhaps bashful, perhaps irreso- 
 lute ; at any rate he does not come quite to the point of 
 saying what he ought to say, and what the young lady 
 desires that he should express in the shape of a formal 
 and distinct proposition. After a long and somewhat em- 
 barrassing silence, young lady takes up, with seeming 
 inadvertence, a card with two strings attached to it, and 
 begins to twirl it. It is but a mere child's toy, quite in- 
 nocent and unmeaning, since it has only a few letters, 
 spelling apparently nothing, on its face. The letters are 
 these S A A. When the card is spun, the coincidence 
 is disclosed that it is inscribed with some other equally 
 unmeaning letters on its back, namely A K P P. 
 These latter, when the motion becomes rapid, combine, 
 through the persistence of vision, with the other letters 
 on the retina of the young gentleman's eye, and they 
 
 ASK PaPa 
 
 form together the words, " Ask papa." The two as- 
 semblages of letters, when thus conjoined, are fraught 
 with obvious significance and suggestiveness. 
 
 And now to apply to the case of the zoetrope the 
 general conclusions on various points which we have 
 
children's toys. 
 
 33 
 
 reached by a course which was not in fact by any means 
 so random and purposeless as it may have seemed to be. 
 
 In the zoetrope, a figure is painted at the end of 
 along strip of paper. It may portray anything you 
 please, as, for example, a man playing a drum, with his 
 arm in a certain position. Close to it on the same strip 
 
 Near the second picture is a third, which is again a 
 similar one, except that it represents the arm in which 
 a change of position has been already noticeable moved 
 a little further still in the same direction as before. A 
 similar set of pictures, alike in all respects, except that 
 the particular variations of a single detail, or of certain 
 details, which began with the earlier part of the series 
 
 D 
 
34 
 
 children's toys. 
 
 are progressively increased along the line, is continued 
 throughout the whole length of the strip. 
 
 The strip is now laid along the interior surface of the 
 revolving cylinder (see woodcut p. 7) which possesses 
 a contrivance for making the figures visible not all at 
 once, but in succession, through loopholes suitably ar- 
 ranged for this purpose ; and the drummer thus comes 
 in his different attitudes, one after the other, into view. 
 As he does so each picture combines and blends in the 
 eye of the spectator with that which has preceded it, 
 and melts into the one which follows it. Thus the 
 general effect of — say three — pictures is that of a 
 drummer passing from one attitude through a second 
 into a third in a very short space of time, so that he 
 appears to be in motion. 
 
 It is necessary to apprehend fully the precise use of 
 the slits through which the figures must be viewed. 
 If, instead of peeping through them, you gaze into the 
 zoetrope over the upper edge of the open cylinder when 
 it is in motion, you only see an indistinct band of colour. 
 This is owing to the figures on the strip being, to the 
 eye, all fused together by their rapid. motion, just as 
 the tints on the chromatic disc were, by a like process 
 which was explained to you just now, melted into one 
 general white. 
 
 It is from a similar cause that when you travel in a 
 quick train the hedges on each side of the railway turn 
 into green torrents, because there are no intervals be- 
 tween the impressions which their component details 
 make upon the sight. The eye is not indulged with 
 even the smallest fraction of an instant's rest, and 
 twigs, branches, and leaves, all, visually speaking, lash 
 
children's toys. 
 
 35 
 
 the retina, one after the other, with such overwhelming 
 rapidity that the optic nerve becomes perforce like a 
 witness giving his evidence in so hurried and tumult- 
 uous a fashion that the judge who has to hear the cause, 
 and whose office corresponds with that of the brain in 
 the case under consideration, is unable to keep up with 
 him, or write down what he says. 
 
 In the zoetrope a main object of the contrivance is 
 that the succession of pictures shall be broken by short 
 intervals, one of which is to be interposed between every 
 two contiguous members of the series. The eye thus 
 obtains such rests as are conceded to it during the 
 periods through which the spaces between the several 
 slits in the side of the zoetrope are passing before it, 
 since these, as presenting no defined images for appre- 
 hension, are equivalent to blank tracts. If these spaces 
 and intervals were long, the eye would possess itself of 
 each figure unconnected with either of its neighbours, 
 and no illusion whatever would arise. But the figures 
 coming rapidly, one after the other, into view, the aggre- 
 gate effect which is presented by them to the spectator is 
 as follows : a figure, say, for example, that of a man with 
 his arms hanging by his side, is first shown. Instantly, 
 or, rather, much less than instantly afterwards, the eye 
 gets the same general figure of the same man, in the 
 same general attitude, but with one of his arms a little 
 raised from his side. Again, less than instantly after- 
 wards, the eye has presented to it the same figure of 
 the man with whom it has already made acquaintance 
 in an attitude which is, as a whole, unchanged, but 
 with the arm which had been previously given as 
 slightly raised from his side now lifted a little more 
 
36 
 
 children's toys. 
 
 still. But this, you know, is the precise character of 
 the spectacle, in all its exact details, which the eye 
 would see if the man who is under observation were a 
 real personage raising his arm. 
 
 The eye is thus imposed upon by a delusive facsimile 
 of what happens in real life. It conceives itself to be 
 beholding a well-known succession of appearances 
 which is inseparably connected with, and is the invari- 
 able result of, a particular sort of motion of an object of 
 a familiar kind with which it is fully conversant, and it 
 naturally accepts this counterfeit presentment as con- 
 clusively indicating that such a motion as the one in 
 question is actually taking place in that object. The eye 
 is, in fact, doubly deceived. For suppose, for example, 
 that the spectacle which it fancies itself to behold in 
 the zoetrope is that of a child jumping up and down over 
 a skipping-rope. It is not true that there is a figure 
 doing anything whatever of this kind. The vertical, 
 that is to say the direct up and down, motion of the 
 figure which is viewed is altogether an illusion, but it 
 has a horizontal, that is to say a sideways, movement 
 as it turns round in the cylinder of the zoetrope which 
 eludes detection by the eye, although it is fully known 
 to be taking place, and is actually within the scope of 
 close and direct observation. 
 
 The nature of the optical deception which occurs 
 may be illustrated by an exactly converse case of error. 
 The same eye which allows itself to be persuaded that 
 a figure in the zoetrope is moving perpendicularly up 
 and down, although in fact its only real change of 
 position is at right angles to that which is attributed 
 to it, will be no less ready to accept the visual imposture 
 
childeen's toys. 
 
 37 
 
 which waves in a storm create when they seemingly 
 roll towards the shore. You probably know that no 
 waves of deep water ever do anything of the kind, but 
 that they simply rise and fall vertically, that is to say 
 over one and the same fixed spot, just as if they were 
 glazed-calico billows at a theatre, where the outer 
 margin of the boundless and raging ocean whence they 
 spring is nailed to a wooden frame a few yards square. 
 
 The case is the same with the waves which may be 
 shaken along a loose string, where also there can, of 
 course, be no transference of particles along their line 
 of undulation. If you go to the Brighton Aquarium, 
 you will see the optical effect upon which we are dwell- 
 ing exhibited by the conger eels. Their favourite 
 position and attitude appears to be that of poising 
 themselves with their noses in the cleft of a rock, and 
 with their long bodies streaming out horizontally back- 
 wards. They constantly send little ripples of motion 
 from their heads to their tails, such as those which run 
 along a flag or handkerchief when floating forth upon 
 a brisk wind. There cannot, of course, be any real 
 transmission of the substance of the eels' persons from 
 their gills to their latter ends. 
 
 You thus find that the eye is a credulous greenhorn 
 of easy gullibility in respect of the facility with which it 
 may be duped. It is so often mistaken about what it 
 supposes itself to see, that hereafter if any one should 
 asseverate some unlikely thing which you may not be 
 prepared to accept as a fact, and should say, " Must I 
 not believe my own eyes ? " you, remembering the 
 zoetrope, will be emboldened to reply, " Certainly not 
 in all cases." 
 
38 
 
 childeen's toys. 
 
 You will have remarked that the zoetrope shows 
 twice over in its action that our eyes possess the 
 faculty of what is called persistence of vision. For it 
 is owing to persistence of vision that each figure coal- 
 esces more or less completely with those on either side 
 of it, which, as we have seen, is the source of the 
 appearance of motion which the trio, when acting in 
 combination, present. It is also due to the same 
 quality of eyesight that although the loopholes which 
 are looked through are of very small width, yet the 
 pictures are seen through them without any sensible 
 interruption whatever, notwithstanding that there is a 
 broad unperforated tract of metal between every one of 
 them and its next neighbour on either side. Hence, as 
 the zoetrope revolves, a screen interposes itself between 
 the eye and the spectacle which is before it during the 
 whole of the time which elapses from the departure of 
 one of the slits from the front of the spectator's nose 
 till the arrival of its next successor at the like situation. 
 Were it not for the persistence of vision we should 
 only see the picture intermittently, or, as it might be 
 expressed, interjectionally. 
 
 You may have noticed that I have endeavoured to 
 explain the effect of the loopholes twice or thrice 
 over. This has been done not by any means inad- 
 vertently, or through any low estimate of your intelli- 
 gence, but designedly, and for a reason which is by no 
 means uncomplimentary to your understandings. The 
 truth is that the matter in question is a very clinic alt 
 one indeed to enter into and realize, and requires to 
 be thought over both long and carefully before it can 
 be thoroughly digested and assimilated by the mind. 
 
children's toys. 
 
 39 
 
 It will be found to be inseparably connected with other 
 subjects of interest, such, for example, as that of the 
 combination of faculties which are essentially necessary 
 to sight in any full sense of the term. 
 
 One of the first things which you were told this 
 evening was that we do not in any real or complete 
 manner see by our eyes. It is the brain which, arguing 
 automatically from its own knowledge, and its stock 
 of previous experiences, puts' its own construction on 
 the images which the eyes present to it. The brain, 
 however, would be unceasingly misled if it were to suffer 
 itself to be cajoled into accepting the pictures which 
 are brought to it from the retina for correct delineations, 
 as they stand, of the objects whose external character- 
 istics they profess to represent. Nor do the pictures 
 give the mutual relations of any set of objects to one 
 another in point of size or position with the least 
 approach to the real truth. They supply nothing more 
 than the materials for founding some judgment on 
 these points. We know that a man born blind, and thus 
 without experience of how the evidence of the eyes 
 should be translated into a veracious representation of 
 fact, would, if he were to be suddenly gifted with sight, 
 " see men as trees walking." The same person would 
 naturally pronounce the sun, if he viewed it through 
 an attic window, to be smaller than the pane of glass 
 through which he beheld it, as, indeed, visually speak- 
 ing it undoubtedly would be as far as he was concerned. 
 In this latter case, the eye in taking the sun and 
 window to be on the same plane, that is to say on the 
 flat surface of the same picture, (which, leaving out of 
 account the correction to be made by the mind, it must 
 
40 
 
 children's toys. 
 
 certainly do,) would also make the trifling error of 
 about ninety-five millions of miles or so in its estimate 
 of the comparative distance from itself of the two ob- 
 jects. 
 
 Visions conjured up by the imagination are said to 
 be seen "-by the mind's eye." Conversely, real and 
 substantial objects, before they can be " seen " in any 
 practical sense, must be viewed, literally speaking, by 
 the eye's mind. Our idea of motion, for example, is 
 not, as Lord Brougham pointed out, a direct perception 
 by sight, but is a deduction from a rapid and automatic 
 process of reasoning founded on data supplied by 
 vision. Similarly we judge of distance by size, and 
 appraise bulk by distance : both are mental processes. 
 We cannot dive farther into the depths of this topic 
 here, but some acquaintance with it is indispensable 
 to a full understanding of the zoetrope. 
 
 Let me take this opportunity of making the remark, 
 which is exemplified by the zoetrope, that although 
 toys are generally rough and simple enough because 
 they answer their intended purposes far better by 
 being thus cheaper, most of them are capable of taking 
 improved and elaborated forms in which they may 
 become valuable instruments of science, and mediums 
 for the exhibition of beautiful and marvellous effects. 
 The prism which we talked about just now, when em- 
 ployed as what is called a spectroscope, opens up to us 
 a whole universe of knowledge of things in the heavens, 
 and of things on earth, and indeed, it may be added, of 
 things under the earth, since it has a special applica- 
 bility to the examination of metals. The spinning 
 cards which were shown to you may be made, by the 
 
children's toys. 
 
 41 
 
 addition of some suitable tackle, vehicles for dis- 
 playing many curious and intricate phenomena. 
 
 In concluding the subject of the zoetrope, let me 
 offer a suggestion for some pictures of a novel kind 
 which might be exhibited in it. Take a very young 
 child; but anybody who is not very old will do. A 
 child will be the best because the changes in early 
 youth of any individual's personal appearance are more 
 rapid and pronounced than in later years. Selecting, 
 then, anyone you please, but a child for choice, photo- 
 graph him or her at several regular intervals. It does 
 not matter how long or short the intervals are, provided 
 that they are frequent enough to prevent there being 
 any very violent difference between the effect of any one 
 given portrait and that which immediately succeeds it. 
 Having obtained a series of such likenesses, arrange 
 them in their proper order, according to their respective 
 dates, along a strip of paper of a shape and size proper 
 for use in the zoetrope. Put this into its place, and 
 spin the apparatus in the usual way. The result must 
 be that as each picture, still bearing traces (which are 
 in fact graven on the spectator's eye) of its more im- 
 mediate predecessors, dissolves into its nearer suc- 
 cessors along the line of portraits, you will have, as in 
 a moving panorama, the progress in life of the individual 
 who is depicted. 
 
 If you turn the cylinder of the zoetrope in a direc- 
 tion opposite to that of the sequence of dates, you will 
 get the curiosity of the seven ages of Shakespeare in 
 their reverse order. If the series of likenesses be suf- 
 ficiently numerous to illustrate every stage in the whole 
 life of an old man, you may within the compass of a few 
 
42 
 
 children's toys. 
 
 moments see him in his gray hair, or bald, as the case 
 may be ; and, as the instrument revolves backwards, 
 and forces Time with unaccustomed footsteps to retrace 
 his track, you will see a crop of hair springing up on 
 the gentleman's head, and growing darker and darker 
 till the period of the fullest bloom of youth, with its 
 rich luxuriance of " thatch." After this you will notice 
 that the locks become again lighter, and then lighter 
 still, and scantier too, as the head whose annals are 
 being pictorially unfolded comes back to the days of its 
 early childhood, till at last it arrives at the very dawn 
 of the first morning of its life, when the little infant's 
 tiny "nut " which has now come into view resembles 
 another sort of nut in respect of its bareness but is a 
 good deal pinker and softer. 
 
 It is said that when a man is drowning it sometimes 
 happens that by one of the marvellous strides which 
 memory, at such moments only, acquires a capacity to 
 take, all the circumstances and actions of his past exist- 
 ence flash upon his recollection in a single instant. We 
 may get, you see, a vision of the same character brought 
 actually to the corporeal as well as to the mental eye, 
 through the means of a rapidly-moving series of photo- 
 graphs such as have been described, recalling the vari- 
 ous successive phases of a man's bodily personality. 
 
 For example, suppose that at one instant a face which 
 is under contemplation in the zoetrope betrays traces 
 of strong excitement, degenerating into anxiety, then 
 brightening up into rapture, afterwards shading down 
 into mere joy, and eventually dissolving into qualified 
 satisfaction. An old man looking at the countenance 
 of his earlier days as it passes through these vicissitudes 
 
children's toys. 
 
 43 
 
 of expression, might possibly be able to interpret the 
 riddle of its alternating oscillations "from grave to 
 gay, from lively to severe/'' in some snch way as fol- 
 lows. " I recognize that aspect of excitement as the 
 sort of mien which I must have worn when I fell in 
 love : the anxiety which follows it betokens the sus- 
 pense of courtship, before Fortune had pronounced 
 whether the enterprise was to turn out prosperously or 
 not. The succeeding rapture indicates acceptance. 
 The joy which ensues proclaims the occasion when the 
 announcement was conveyed to me that my house was 
 now gifted with a son and heir. The transition of that 
 joy into a display of less ardent satisfaction marks no 
 doubt the ebbing of the springtide of delight which set 
 in when I was made acquainted with the rather startling 
 fact that in this instance the words " son and heir " 
 had a richer significance than usual, and meant twins, 
 or even a triplet, and when, by way of evidence that 
 such was the meaning which belonged to the expression 
 in the present case, they all began to scream together." 
 
 But without the protracted, trouble which would be 
 required for obtaining a succession of portraits of any- 
 body at certain intervals, the same kind of experiment 
 may be shown in many other ways. Take, for example, 
 the bud of a flower, and have a fresh sketch of it made, 
 either by a pencil or photography, every few days, or 
 oftener, according to the greater or less rapidity with 
 which it advances towards maturity. The bud may 
 remain on its tree, or be put in water, if it will expand 
 there. Insert the series of sketches thus obtained in 
 a zoetrope, in the manner which has been already 
 described, and on setting the toy in motion the appear- 
 
44 
 
 children's tots. 
 
 ance presented to the eye will be that of the bud ex- 
 panding into a full-blown flower, or, if the cylinder be 
 turned the other way, the effect, of course, will be just 
 the opposite, namely, that of the flower folding itself 
 up, and retreating within the coat of its original bud. 
 
 One more illustration of a course of development, or 
 of the reverse process, may be suggested. Select an egg 
 whose inmate is just about to burst through the shell, and 
 get a picture made of it; or you can start, if more con- 
 venient, at a rather later stage in the chick's life when it 
 has escaped from confinement in the cramped premises 
 wherein it was born, and stands forth proud and free as 
 a soft little ball of yellow plush, not as yet endowed with 
 the dignity of a tail, and supported on a pair of spindle 
 shanks so thin that they are only discernible in very 
 clear weather. Procure, as before, your chronological 
 gallery of portraits of the chick, terminating with a 
 cock or hen, as the case may be, arrayed in full plumage. 
 You will now, with the aid of the zoetrope, be in a 
 position to exhibit, within almost the compass of a 
 single glance, the whole course of a fowl's existence 
 from the " welcome little stranger" stage — the juncture 
 when it escapes the liability to which, as long as it re- 
 mains within its shell, it is exposed, of being poached, 
 to the time when its immediate prospects become 
 associated with bread-sauce. Now when you go home 
 this evening, and your friends ask you about the lecture, 
 you will be able to say (at least, so it is to be hoped) 
 that you heard some things that were new to you ; and 
 if you are asked for an example, you can reply that the 
 lecturer told you how to put back a full-grown barn- 
 door fowl into an egg. 
 
childken's toys. 
 
 45 
 
 It may be mentioned, as a concluding observation 
 upon the subject of persistence of vision, that were it 
 not for this quality of our eyesight, a landscape, even 
 when steadily gazed upon, would be but very imperfectly 
 beheld. This point would take a little time to explain, 
 as it is not a simple one, and I therefore remit it to the 
 consideration of any of you who may have sufficient 
 enterprise to investigate it for yourselves. 
 
CHAPTER II. 
 
 E have been walking up to this point on a 
 somewhat rough and stony road, and some 
 of you may perhaps be a little bit footsore, 
 and require a short rest. In other words, 
 we have been treading a path of inquiry which is not 
 quite, perhaps, at every point of its course, the very 
 smoothest which could be followed, so that you may 
 like to turn for a time to something or other which 
 has nothing to do with so stiff a science as that of optics. 
 Suppose, therefore, that we take a doll into our hands, 
 and see if it has anything to tell us. At first sight a 
 doll might be imagined to be barren of interest for 
 grown-up people, since it does not " work " as optical 
 and mechanical toys do, but is, like most young 
 ladies, an inanimate, mindless, though rather orna- 
 mental sort of object; a pink- and- white structure, 
 fashioned after the semblance of a real human 
 being. Yet there is a great deal which might be 
 said about dolls, as will appear by the following 
 anecdote, the truth of which is within my own per- 
 sonal knowledge. 
 
 When I was an undergraduate at Trinity College, 
 
children's toys. 
 
 47 
 
 Cambridge, Lord Macaulay, the celebrated "historian, 
 who was a member of the College, and very much 
 attached to the place, used frequently to come and 
 dine in our Hall. Lord Macaulay teemed with know- 
 ledge of all sorts and kinds on all manner of sub- 
 jects. He reeked with information from the crown 
 of his head to the soles of his feet. He was also of a 
 very lively disposition, and a prodigious talker. The 
 result of the conjunction of these particular qualities 
 was that, whatever subject of conversation might be 
 started at the dinner table, he used to go off upon it 
 " at score/' without break or pause, his discourse being 
 a monologue, since it afforded no chink or opening 
 through which a single word could be edged in by any- 
 one else. Lord Macaulay's self-abandonment to the 
 impulses of his natural vivacity and fecundity of talk 
 was like the gallop of a thoroughbred horse who 
 takes the bit between his teeth and bounds along, 
 deaf and insensible to everything but the promptings 
 of his own impetuosity, till he has run himself clean 
 out of breath. The Dons, as they are called, that is to 
 say the tutors and authorities of the College, among 
 whom Lord Macaulay sat, got tired of the perpetual 
 wagging of his Lordship's tongue, so they formed a 
 conspiracy for muzzling him through the manoeuvre of 
 choosing some theme for conversation on which it was 
 impossible, as they confidently supposed, that he could 
 find anything whatever to say. And the topic which 
 they selected out of the whole universe of conceivable 
 subjects, as being the one from which the most ingeni- 
 ous inventiveness could not possibly contrive to extract 
 any material for discourse, was that of dolls. But they 
 
48 
 
 chjldken's toys. 
 
 had mistaken their man. For Macaulay was so brim- 
 ful of thought and knowledge about dolls that it took 
 the whole rest of the evening, from the time of the 
 first mention of the word, to allow his flood of talk 
 upon them to run itself off. 
 
 Now this anecdote is suggestive. It shows that if 
 there is anyone among you who would like to write an 
 essay on a popular subject, which would have all the 
 charm of being new as a literary theme, and which 
 would at the same time be susceptible of interesting 
 and instructive treatment, a more promising and fertile 
 text than that of dolls could hardly be chosen. I can- 
 not address myself fully to the enigma which it presents 
 for solution, which is this : What is the secret of the 
 absorbing and passionate devotion which dolls inspire in 
 the breasts of little girls ? It is no answer to reply that 
 little girls are fond of dolls for the same reason that, ac- 
 cording to Dr. Watts, dogs delight to bark and bite, 
 " for 'tis their nature to," for the point of the inquiry 
 is " Why is it their nature to ' ? " 
 
 Some explanation has been attempted to be given 
 by Mr. Herbert Spencer in his book called " First Prin- 
 ciples." It would be idle to enunciate Mr. Spencer's 
 conclusions to anyone not accustomed to read philoso- 
 phical works dealing with inquiries into obscure and 
 complex sources of physical and mental phenomena, 
 since there could be no hope that they would be 
 really understood even if they were to be put into the 
 simplest language in which they could be conveyed. 
 There may perhaps be some present who may be 
 interested by them, so that I will by two or three sen- 
 tences, addressed to those few persons only to whom 
 
childken's toys. 
 
 49 
 
 they will be intelligible, indicate the drift of Mr. 
 Spencer's theory. Play he views as a simulation of 
 activities conducing to the ends of life. He supposes 
 that in the process of evolution faculties become de- 
 veloped beyond the range within which they are neces- 
 sary to subserve the functions of the organism, and 
 that in this case the unemployed energies seek an 
 artificial vent. Very frequently this discharge of re- 
 dundant energy takes the form of conscious imitation 
 of the useful actions. Thus, for example, one sees in the 
 devotion of little girls to dolls, and in boys' games of 
 chase, an amusing mimicry of the serviceable actions 
 of adult life. This theory applies, as will be observed, 
 to the character of the pleasure which is yielded 
 by a great variety of toys, such as, for example, 
 boxes of bricks, horses and carts, and bows and 
 arrows. 
 
 To descend from these altitudes of philosophy, which 
 most of you, no doubt, find to be, like other high 
 peaks, somewhat cold and rugged, to the smooth 
 pastures of common life below, where our path will be 
 softer to the tread. Did you ever hear how an 
 American writer began a poetical effusion about babies 
 with the rhapsody — " How beautiful is babes ! so 
 small, and yet so like human bein's ! '* A fond mother 
 would probably feel aggrieved if anyone were to tell 
 her that her baby was only " like " " a human beinV 
 She would probably exclaim, as an Irish mother is said 
 to have done to someone who evinced an inadequate 
 appreciation of the charms of babies, " Ah, Sir, it's, 
 plain yon never were a mother ! " But it may with 
 truth be said in praise of dolls that they are " small, 
 
 E * 
 
50 
 
 childeen's toys. 
 
 and yet like human bein's," since, when new, they 
 ought to possess, as an indispensable requisite for 
 giving proper satisfaction, a full and accurate sem- 
 blance of humanity. 
 
 No doubt a doll, when it has once secured its 
 owner's affections, will retain them long after it has 
 lost its bloom of fresh paint, and when it is bereft of 
 every rag of clothing, and its limbs have been re- 
 duced to mere flabby bags, owing to the escape from 
 them of the bran from which their plump, sausage- 
 shaped proportions were derived. And a little girl 
 will still cling with an unalterable affection, which is 
 almost touching, to what was once a wooden doll, but 
 has now degenerated down into a battered and disre- 
 putable plug of wood. " Around the dear ruin each 
 wish of her heart entwines itself verdantly still." 
 But a doll, to win approval, must, in its original and 
 unimpaired condition, resemble such people as the 
 little girl who is to be its possessor is accustomed to 
 see. Black dolls would never be accepted here, but 
 they are largely manufactured in England for export to 
 America as play-things for little negro girls, who view 
 a dark skin as of the orthodox and only proper colour. 
 Blue-eyed dolls are favourites in this country, and they 
 have been more fashionable than ever, according to the 
 experience of toy merchants, since the time when the 
 present Queen came to the throne. They might 
 naturally be expected to be popular in the northern 
 regions of Europe where fair complexions and blue 
 eyes prevail. In Italy and Spain, dolls with black eyes 
 are the most approved, as being more in accordance 
 
children's toys. 
 
 51 
 
 with what is usually seen in real life in those coun- 
 tries. 
 
 The facts which have just been stated about dolls' 
 eyes have been gathered from no less grave an authority 
 than that of a Blue-book of the House of Commons. 
 Some little time ago a glass manufacturer of Birming- 
 ham was called as a witness before a Select Committee 
 of the House of Commons to give evidence on certain 
 subjects relating to his trade, and incidentally to these 
 he mentioned the particulars which have been stated 
 with reference to the comparative popularity in different 
 countries of the various colours of dolls' eyes. The 
 manufacture of these articles is a not altogether incon- 
 siderable business, since the same witness who has 
 been already quoted said that he had received on one 
 occasion an order for five hundred pounds' worth of 
 such eyes, and it may be of course assumed that a 
 number of other people in the same trade had had 
 similar demands made upon them for satisfying the 
 requirements of the doll market. 
 
 The heads of the better class of dolls, and such por- 
 tions of their arms and legs as are to be visible to the 
 public after they are dressed, are usually composed of 
 papier mache, which is paper made into a soft pulp, so 
 that it can be moulded, while wet, into any shapes which 
 may be desired. The faces are formed from wax, or 
 from papier mache covered with enamel and var- 
 nished. 
 
 Dolls of the less aristocratic order, whose lot is to be 
 cast in cottages, are simply made of wood, and of these, 
 again, there are two grades, those, namely, which have 
 
52 
 
 children's toys. 
 
 their full complement of limbs of the orthodox type, 
 working on joints which, although they move uneasily, 
 as though stiffened by chronic rheumatism, are still 
 practicable, and those whose persons are for cheapness 
 formed of mere sticks covered with bits of rag, which 
 the purchaser is invited to consider as representing 
 attire. 
 
CHAPTER III. 
 
 BEE is our old familiar friend the tumbler, as 
 he is called, which is rather an inappropriate 
 name to give to him, because if there is any- 
 one particular thing in the world which he 
 certainly does not do, and cannot be made to do, it is 
 to tumble. All the most cherished principles of con- 
 
 duct on which he acts are inflexibly opposed to tum- 
 bling. He is complaisant enough to the extent of 
 bowing readily, but persist as you may in knocking him 
 down, and in trying to make him stay down, he evinces 
 
54 
 
 children's toys. 
 
 an unconquerable obstinacy in always resuming an erect 
 posture. By indulging a trifling fancy we may discern 
 in the behaviour of this toy a typical illustration of 
 the Mark Tapley spirit of indomitable cheerfulness 
 raising a man's head again and again as often as he has 
 been bowed by depressing influences. 
 
 Now what particular property is it in the consti- 
 tution of the tumbler which leads him to comport 
 himself as he does ? Somebody, perhaps, will answer, 
 " Because the weight of the figure is in its lowest part." 
 Granting that the fact is so, a reply will still be wanted 
 for the further inquiry which necessarily follows as to 
 why the circumstance in question obliges the tumbler 
 to stand upright. " Because," it will be rejoined, " the 
 heaviest portion of the figure being in its nethermost 
 extremity, that region, naturally, by its own weight, 
 sinks to as low a position as it can reach, and stays 
 there ; and when the base of the tumbler is thus brought 
 as close as possible to the surface of the table, the 
 head cannot but be highest, and the whole body up- 
 right." 
 
 This explanation is perfectly sound as far as it 
 goes, but are you quite sure that you fully understand 
 its why and its wherefore, and all that it imports ? 
 For captious critics might take exception to the 
 allegation that the tumbler keeps upright because the 
 lower part, being weighted, naturally assumes the 
 lowest position. They might say that the word 
 " naturally " seems to imply that heavy things have 
 a tendency to fall downwards of their own accord, 
 that is to say, that they are actuated by something 
 like a will and habit of their own. They would add 
 
children's toys. 
 
 55 
 
 that such, a representation as this is objectionable, as 
 being likely to give rise to mistake or obscurity as to 
 the real fact, which is of an exactly opposite character, 
 namely, that heavy things so far from moving at all by 
 their own inclination, independently of compulsion on 
 the part of some distinct agency outside themselves, 
 seem to do their best to resist disturbance, and that 
 the degree of their reluctance to stir exactly corre- 
 sponds with the amount of their weight; so that a pro- 
 portionately greater force would, accordingly, have to 
 be applied to induce a ponderous body, although un- 
 supported and quite untrammelled, to tumble earth- 
 wards than would suffice to start and bring down a 
 lighter object. 
 
 This statement is true, since heavy bodies have 
 in effect what is called a " vis inertiae," or as it may 
 be translated, a strength of immobility, in propor- 
 tion to their weight. The phrase in question may be 
 demurred to as being vague, and therefore undesir- 
 able, and as even conveying, in one sense in which it 
 may be taken, an idea which is downright inaccurate, 
 since it seems to suggest energy rather than apathy. 
 It might be construed as importing what is not true, 
 namely, that inanimate bodies, being constitutionally 
 lazy, exercise of their own pleasure a force created of 
 their own will which they oppose to any agency which 
 seeks to disturb their rest. 
 
 Leaving these ambiguities of language which it was 
 as well just to notice in order to prevent their intro- 
 ducing some muddiness or other into our ideas, which, 
 to be worth anything at all on any subject whatsoever, 
 must, as a first essential necessity, be quite clear, we 
 
56 
 
 children's toys. 
 
 may proceed to say that the force which makes heavy 
 things fall is that which is so familiarly known as " the 
 attraction of gravity/' Now the attraction of gravity 
 being one of the most important actors on the world's 
 stage, and not only that, but one of the grand Poten- 
 tates by whom the Universe is swayed and regulated, 
 it will be an interesting subject for consideration. If 
 this toy be taken as a text, a discussion on gravity will 
 be strictly apropos to it, since the whole performances 
 of a tumbler are exclusively concerned with the action 
 of the force in question. 
 
 Every single thing of every kind which the world 
 contains is unremittingly acted on and kept in its place, 
 or moved from it, as the case may be, either directly or 
 indirectly, by the attraction of gravity. So is the world 
 itself, and as far as we know so also are all the stars. 
 Everything about us, together with our own selves, and 
 everything in the heavens, would be sent flying anyhow 
 and any whither, in undignified and tumultuous confu- 
 sion through space, and there would be a general col- 
 lapse and crash of the whole universe, if the power of 
 the attraction of gravity were to be suspended, or even 
 in the least degree relaxed, for a single instant. It is a 
 matter, therefore, which is worthy of our attention, as 
 constituting a material element in the stability of the 
 general arrangements of creation upon which our exist- 
 ence at every moment depends. If you comprehend 
 the mode of action of this great force you will under- 
 stand the working of this toy, and to put the matter 
 both ways for the purpose of impressing it on you the 
 more, it may be added that until you are thoroughly 
 capable of understanding the springs of conduct of this 
 
children's toys. 
 
 57 
 
 simple plaything, you can form no idea of what the 
 attraction of gravity is, nor can you make a single 
 step towards the acquisition of even a rudimentary 
 acquaintance with any one of a whole catalogue of sub- 
 jects of which no one of intelligence should remain 
 ignorant. 
 
 Now, first of all, what does the expression the " at- 
 traction of gravity" mean? Gravity means weight, 
 and attraction mean cc drawing towards " ; the phrase, 
 therefore, implies that everything which has weight en- 
 deavours to draw every other thing which has also 
 weight towards itself. From this the corollary, or logical 
 consequence, obviously follows, that every such source 
 of attraction is, in its own turn, exposed to like influ- 
 ences. If this be true, and it certainly is so, then, since 
 all of us who are present weigh something, a force of 
 attraction must reside in each of us, and be exercised 
 upon the rest of the assembly. Everyone here is 
 actively, though unconsciously, exerting a force upon 
 every other individual of our party, and upon every ob- 
 ject in this room, and also upon the walls, floor, and ceil- 
 ing. Moreover we are all of us, at this very moment, 
 keeping this force at work upon all other rooms, and 
 their contents ; but we may very well confine our at- 
 tention to the state of things at the particular spot where 
 we are met. 
 
 Now why, if it be true that this mutual . attraction 
 invites and urges a general and close approach, do 
 we not each of us glide by one consent into our next 
 neighbour's arms, and stay there for ever, or why 
 don't we at any rate feel an impulse to do so ? Be- 
 cause we are restrained from any such procedure by 
 
58 
 
 childeen's toys. 
 
 other forces which, tend to drag us in the opposite 
 direction. You attempt to draw me towards you hori- 
 zontally, but the ceiling strives to hoist me upwards ; 
 the floor tries to haul me down, and the walls to pull 
 me four ways at once. These forces neutralize one an- 
 other, that is to say, they counteract and thus destroy 
 one another's effect, so that I remain still just as if no 
 force at all was acting on me, like the donkey who stood 
 motionless between two bundles of hay of equal tempt- 
 ingness. If the forces were strong enough, and the 
 coherence of the various elements of my personality 
 less robust than it is, I should be torn in pieces, and a 
 general scramble would take place for the fragments of 
 the bone of contention which I already constitute. 
 
 Conceiving, however, the general result of all these 
 warring attractions, when acting at any particular mo- 
 ment on some given object, to be such as would cause 
 it to stir if it were not restrained from so doing, still, 
 no locomotion may in fact ensue. For with the very 
 first inception of any start, and indeed before any overt 
 act of this kind can be even initiated, another force, that 
 of Friction, with which we shall have to make some 
 further acquaintance hereafter, is called into being, and 
 has to be reckoned with. The force of friction is one 
 which varies in energy with the particular conditions 
 which give birth to it, but whatever the amount of its 
 power may be in any specified case, the whole of it is 
 invariably put forth in direct opposition to motion. If, 
 therefore, the balance of the various attractions of grav- 
 ity which are at this moment contending for the mastery 
 over any object, say the table before us, were to be in 
 favour of its transference to the other side of the room, 
 
childken's toys. 
 
 59 
 
 the victorious influence would still have to settle ac- 
 counts with friction before it could generate any prac- 
 tical effect. 
 
 But, you may ask, is it really true, as was alleged 
 just now, that all bodies having weight attract one 
 another ? It can be shown in a thousand ways that 
 such is the case. The following is a common proof, 
 which is reached by actual experi- 
 ment. Suppose that you have a 
 high cliff overhanging the sea, or 
 a plain, and that from its edge you 
 drop a string with a weight at its 
 end, thus forming what is common- 
 ly called a plummet line, and allow 
 this to dangle free in the air, so that 
 it is easily to be swayed in a lateral 
 direction by any sufficient force. 
 It will be found that the string 
 will not hang perpendicularly, but 
 slanting a little towards the cliff, 
 because this latter, having very 
 great weight, will attract the leaden 
 ball and drag it towards itself. In 
 this case, you see, the cliff is enormously heavy, that 
 is to say it has a great attractive power, which is not 
 counteracted by anything immediately opposite to it, 
 and equally close, on the other side of the string. 
 
 Why gravity attracts as it does nobody knows, so 
 that of course I cannot explain it. But although we 
 cannot detect the why, we can to some extent mark 
 the how, that is to say the mode or course in which the 
 force in question acts. To understand this, a clear no- 
 
60 
 
 childken's toys. 
 
 tion of wliat is meant by the expression " the centre of 
 gravity " must first be acquired. 
 
 The centre of gravity of any body is the point 
 about which all the parts of that body balance one 
 another in weight. It follows from this definition, as a 
 little consideration will show, that if the point in ques- 
 tion be suspended from, or propped by, some adequate 
 support placed in a vertical line above or below it, the 
 body will remain at rest. A further consequence will 
 also be found to be involved by the terms of the same 
 definition, namely, that if the point in question be not 
 thus sustained, it will immediately make its way towards 
 the lowest position which it can reach, and will con- 
 tinue to pursue this course until it is definitively arrested 
 by some impediment which it is unable to overcome. 
 When it is thus brought to a standstill, the body of 
 whose gravity it is the centre will obviously remain at 
 rest. For its several parts, balancing one another 
 round its centre of gravity, neutralize whatever inde- 
 pendent and separate power any one or more of them 
 might otherwise possess of causing further motion. 
 Their various forces are, in effect, as you see, all spent 
 upon a combined effort to depress the centre of gravity, 
 but this, having got as far down as it can go, is no 
 longer amenable to coercion. 
 
 To illustrate by an example what is meant ; take 
 any object you please; but something of an extremely 
 simple form, such as, for instance, this board, will be 
 the most convenient. Its thickness, being very small 
 in comparison with its length and breadth, may be neg- 
 lected, so that the two latter dimensions only need be 
 regarded. Make a hole in it anywhere, and then sus- 
 
children's toys. 61 
 
 pend it, as may be readily done by this 'pin, in any such 
 manner as that it may swingwith perfect freedom. Since 
 
 it is thus put at liberty to hang in whatever posture may 
 be most in conformity with the general result of the 
 forces which govern its movements, it necessarily as- 
 sumes the particular position in which the weights of the 
 parts on the right and on the left of the pin respectively 
 balance one another. If the two sides of the board did 
 not mutually counterpoise, the heavier would go down, 
 and in so doing would pull the lighter up, just .as hap- 
 pens with a pair of scales when the weights in the two 
 saucers are unequal. And the board, like the scales, * 
 would be kept in continuing unrest until a balance was 
 established. But the board, as you see, now hangs 
 contentedly quiet, which shows that its centre of 
 gravity is at some point in the perpendicular line be- 
 tween the pin and the ground. 
 
 Now suspend the board from any other point in it, 
 taken at random, such as this, for example, and let it 
 hang freely as before. Thus. After swinging a little, 
 like a pendulum, till the result of the forces which are 
 in action has been determined, it becomes stationary 
 
62 
 
 children's toys. 
 
 and at this juncture its centre of gravity must, by the 
 same reasoning which was employed just now, be some- 
 where in this perpendicular line let fall from the pin 
 towards the floor. But we have already seen that it 
 is also in this first line, and if it is to occupy a place 
 in both, it can only do this by being situated at the sole 
 exact point which is common to both lines, that is to 
 say where they cut one another, which is here, at c g. 
 
 Now the force which anything exerts by its weight, 
 that is, in other words, the attraction which it exercises 
 by means of its gravity on other objects which also have 
 weight, behaves precisely as if it acted from the centre 
 of gravity of the body whence it emanates. So that 
 in estimating the effect which this force does, or must, 
 produce, it may be considered as operating just as if the 
 centre of gravity of the body which generates it were 
 its actual and exclusive source. This is, virtually, the 
 real fact. 
 
 Hemember all this time that we are speaking of the 
 centre of a body's gravity, which is quite a different 
 thing from the centre of the same body's form. The 
 centre of a body's weight, or gravity, need not by any 
 means be at the same point with that of the middle of 
 its figure. The body, as in the instance of the per- 
 sons of men and women, may be made up of parts 
 consisting of different materials, some of which may be 
 heavier than others, and if this should be so, the centre 
 of the weights of the several portions taken together 
 will not necessarily fall at the middle of the whole 
 group. In many cases, indeed, the centre of gravity 
 of an object is not within the external surface of its 
 body at all. The centre of gravity of a ring is at 
 
children's toys. 
 
 63 
 
 about the middle of the space which is left open for 
 the finger, and that of a man's hat is somewhere or 
 other in the tract which is occupied by the wearer's 
 head. It is true that in the case of a symmetrical 
 figure, such as a round ball or a square die, the centre 
 of its gravity coincides with that of its figure if the 
 object be homogeneous, that is to say if it be wholly 
 composed of one material only, or of materials which 
 are of uniform heaviness throughout, because in such 
 instances as this the weights of the various parts are 
 manifestly disposed in precisely equal proportions all 
 round the middle of the space which they occupy. 
 
 Let me now give you an illustration of the course 
 in which the attraction which is exercised by the 
 
 gravity of anything and everything acts, as has been 
 described. Here is an umbrella, and here, at a short 
 distance off, is a pea. What do we now know of their 
 relations to one another ? This, that the umbrella is 
 attracting the pea and the pea the umbrella, and that 
 if they were not forcibly held back by other agencies 
 they would move towards one another, and remain 
 locked in a perpetual embrace. 
 
 This opportunity may be taken for adverting to a 
 
64 
 
 children's toys. 
 
 main fact and feature of the subject which we are upon, 
 which is this, that the force of the attraction of gravity 
 is proportionate to the distance through which it oper- 
 ates, as also to the quantity of matter, called the 
 " mass/' which exerts it. The latter condition is the 
 one with which our present inquiries have immediately 
 to do. In lead, the particles which compose the metal 
 are packed together far more closely than is the case 
 with the materials which make up a feather, so that the 
 former exercises a much more powerful attraction, bulk 
 for bulk, than the latter does. Similarly, the umbrella 
 brings into play a greater force of attraction than is 
 wielded by the pea from having a larger quantity of 
 material in its personality. The attractions with which 
 the umbrella and pea operate on one another are re- 
 ciprocal, but, as we have seen, not equal in power. 
 
 Suppose now that the pea were quite free to move, 
 and to go to the umbrella, at what point would it join 
 it ? At, or as near as possible to, the centre of gravity 
 of the umbrella, since, as was stated just now, the 
 whole attraction of the umbrella may be regarded as 
 if it were concentrated at, and worked from, that 
 point. Why is this ? Because the attraction of the 
 umbrella as a whole is, of course, and must be, no- 
 thing more nor less than that of its mass ; and that 
 of its mass is the sum of the attractions of the several 
 component items of its various parts, each of which 
 is, in its way, a magnet. If these separate forces of 
 attraction be represented upon paper by lines traced 
 along such tracks as they must really pursue, the 
 general pull in which they unite will be visibly seen to 
 be necessarily of the character which has been assigned 
 
children's toys. 
 
 65 
 
 to it. The forces are, of course, innumerable, since 
 each little several atom of the wood, steel, and silk of 
 the umbrella is in itself a tiny loadstone. If, therefore, 
 every such force were to be separately represented, the 
 lines would be absolutely countless. But a true idea 
 may be given of the general tendency of the whole by 
 the delineation of a few of them as indicators of the 
 proceedings of themselves and of their more immediate 
 companions. 
 
 Now conceive the lines which we have drawn to be 
 strings all pulling the pea at once. You can see at 
 a glance that the result of the combined tug, if not 
 rendered of none effect by friction or by some other 
 counteracting agency, would be to land the pea at a 
 spot about half way up or down the length of the 
 umbrella. A little consideration would show you 
 that the point in question must necessarily be the 
 centre of gravity of the umbrella. And a little further 
 examination of the matter would demonstrate no less 
 clearly that the precise road which the pea would be 
 bound to take would be along a straight line joining 
 its own centre of gravity with that of the umbrella. 
 
 The conditions which would govern the procedure 
 of the pea would, if allowed free play, regulate the con- 
 duct of any other body moving under the influence of 
 the attraction of u gravity towards an object heavier 
 than itself. The path to be followed could be no other 
 than the shortest cut to be found between the two 
 centres of gravity of the objects concerned. 
 
 And now let us consider the application of this 
 general and unvarying law to the particular case of the 
 attraction which the earth exercises by means of its 
 
66 
 
 children's toys. 
 
 gravity upon everything on its surface, for this inquiry 
 is one which forms an indispensable preliminary to any 
 real examination of the action of the tumbler. 
 
 Our globe is, roughly speaking, a sphere, or solid 
 ball, so that its centre of gravity is, as we saw just now 
 must be the case, identical in situation with the middle 
 of its mass, that is to say, at the very innermost heart's 
 core of its substance. Everything, therefore, which 
 the earth's gravity can affect is attracted towards this 
 centre. Now draw a circle, thus, to represent the 
 
 world, or a section of it made through its waist, and 
 say that England is hereabouts, at the top of the 
 diagram, and imagine that at this point there is an 
 apple tree with an apple on it, and conceive the latter 
 to be ripe, and to fall from its stem. Why, as Newton 
 is said to have asked himself, does it fall ? It is not 
 accurate, as you have already learnt, to talk or think 
 about falling as if that were an act w 7 hich the apple, 
 
children's toys. 
 
 67 
 
 or anything else, does, or can do, of its own accord. 
 You will remember that nothing ever moves, or stops 
 moving, except under the compulsion of some force. 
 An apple, when its stalk gives way, would, as far as any 
 will of its own could be concerned, stay where it 
 already is, but it is drawn towards the centre of the 
 Earth by the attraction of gravity. When it reaches the 
 ground, it there encounters a bar to further progress, 
 but if it were not thus arrested, it would never stop 
 till it had ensconced itself at the nucleus of the Earth's 
 mass, which is about 4000 miles underneath the spot 
 where we are standing. 
 
 Now if England be taken to be at the point of the 
 circle which we assigned to it, then New Zealand will be 
 nearly at the opposite position, at the bottom, that is, 
 of the diagram, and an apple falling from a tree in that 
 country will tumble upwards. Similarly if China be 
 hereabouts to the right, and Peru somewhere in this 
 direction on the left, apples dropping respectively from 
 trees in those parts would fall horizontally. 
 
 Here you have the plainest possible demonstration 
 that whenever anything which is free to move obeys 
 the attraction of the Earth, or^ as it is popularly ex- 
 pressed, falls, it does not tumble in any accidental 
 fashion, but is simply pulled, as far as it can go, to- 
 wards the centre of the globe. Loose talk about the 
 natural tendency of bodies to fall, if the terms of such 
 language be examined, does not even amount to a pre- 
 tence of explaining anything, since the words " up- 
 wards " and e( downwards " are, of course, merely 
 relative expressions, indicating change of situation 
 with reference to something or other, and not any 
 
68 
 
 children's toys. 
 
 absolute direction considered independently. u Up- 
 wards/' in and for whatever locality it is used, is con- 
 ventionally understood to imply retreat from the Earth, 
 and " downwards 99 approach to it. Since these mean- 
 ings are respectively attributed to the terms in question 
 for all spots on the surface of the world, and through- 
 out all the various attitudes which the globe assumes 
 in the course of its orbit, they can plainly have no 
 more than the restricted signification which has been 
 mentioned. For if their import was not taken to be 
 thus limited, it would comprise changes of place in 
 all directions which are conceivable, and of which half 
 the number would severally be diametrically opposite 
 to the other half. Lines of possible movement are, as 
 need scarcely be observed, absolutely infinite in number, 
 
 so that the expressions which have been criticised would, 
 if not interpreted in the narrow sense which has been 
 
children's toys. 
 
 69 
 
 pointed out, be wholly devoid of any real meaning 
 whatever. 
 
 For reasons which have now become obvious the 
 saucers of a pair of scales do not hang with their 
 centres in a perpendicular line below their respective 
 points of suspension if the pillar which supports the 
 beam be regarded as vertical. That is to say, lines 
 drawn from those centres to the beam-ends above them 
 are not parallel to one another, or to the scale post, 
 but as they approach the ground they make some slight 
 convergence. This deviation from parallelism, although 
 it is so infinitesimally small as to elude any observa- 
 tions which our senses can bring to bear on it, and 
 defies any tests by which we might endeavour to 
 appraise it, has nevertheless a true existence. Lines 
 drawn as supposed would meet at the centre of the 
 earth, and so of course would the saucers if they could 
 swing so far. 
 
 It has been stated that the centre of the globe is 
 the seat of the whole attraction of gravity which the 
 entire mass of our world exercises. The thorough as- 
 similation, in medical phraseology, of this fact by the 
 mental digestion may be promoted if it be administered 
 in another shape in which it will be readily taken up by 
 the intellectual absorbents. The attraction of gravity 
 is found by experiment to be governed by a particular 
 law to which we referred just now, and to which it 
 conforms, under all circumstances whatever, with strict 
 and implicit obedience. This Ordinance of Nature, 
 when expressed, for simplicity's sake, in the most 
 general terms possible, is as follows, namely, that the 
 attraction of the gravity of any given mass wanes 
 
70 
 
 childken's toys. 
 
 according to a certain well-ascertained scale of degrees 
 which is in precise correspondence with the length of 
 the distance through which the force acts. Now if the 
 surface and not the centre of the Earth were to be 
 taken as the source whence attraction emanates, re- 
 sults inconsistent with the law in question would be 
 given by practical experiments founded on such an as- 
 sumption as this, showing that an erroneous basis of 
 calculation had been laid. 
 
 We have seen that the centre of gravity of any, and 
 every, body is that point about which, if it be sup- 
 ported, the whole mass will balance, and therefore rest 
 quiet and contented. We have also seen that if this 
 point be not supported, it will descend to as low a posi- 
 tion as it can reach, travelling along the straight road 
 leading from its own position for the time being to- 
 wards the centre of the earth. Let us take a couple of 
 instances to show how this occurs in actual practice, 
 and with what results. 
 
 Here we have a three-cornered board of the shape 
 of a pyramid. Since it is of a regular figure, and of 
 one uniform substance, its centre of gravity (leaving 
 out of account its thickness which is so small as to be 
 immaterial) will be at the middle of its surface. Set 
 
CHILDREN^ TOYS. 
 
 71 
 
 this pyramid upright upon its base — thus — at the edge 
 of the table. Suspend a string, with a weight at its 
 lower end, from the centre of gravity of the pyramid 
 in such a manner that it may hang quite free. The 
 weight is bound to get as near to the centre of gravity 
 of the earth as it can, and the string by which it hangs 
 must thus represent part of a straight line which, if it 
 were to be continued sufficiently far, would join the 
 centre of gravity of the earth with that of the pyramid. 
 
 The pyramid remains at rest. Why ? Because its 
 centre of gravity is supported by what may be regard- 
 ed as a vertical prop, constituted by a line of particles 
 which are a portion of the substance of the pyramid, 
 and which, as it were, form a pillar whose base rests upon 
 the table. If you tilt the pyramid a little up on one side, 
 you lift, as you see, the lower end of the prop from the 
 table. The pyramid, therefore, will not continue at rest 
 after your hand is withdrawn, since its centre of gravity, 
 havingbeen deprived of the support which it gained from 
 the table through the prop, will now move downwards, 
 till the original conditions of stability have been restored. 
 The pyramid may be considerably tilted, yet it will still 
 continue to resume its first position as soon as per- 
 mitted to do so, provided only that it is not made to 
 bear over to one side to such a degree as that the line 
 dropped perpendicularly from its centre of gravity falls 
 beyond the extremity of the base in that same quarter. 
 When that occurs, the attraction of gravity combines at 
 once with the lateral inclination coming from the tilt, 
 instead of counteracting it, and helps to bring the 
 pyramid down by pulling it round over the terminal 
 point of its base, turning it, as it were, upon a pivot. 
 
72 
 
 children's toys. 
 
 A pyramid, therefore, when standing on its base, 
 has such a figure and "pose 39 as are calculated to impart 
 to it a resolute conservatism of attitude, since the effect 
 of any disturbance of its equilibrium, provided that 
 this does not exceed a certain definite limit, is to excite 
 an opposing and restitutive action on the part of 
 gravity. A body so circumstanced in respect of its 
 balance is said to be in a position of " stable equili- 
 brium."" 
 
 It is quite unnecessary to advert to the obvious 
 reasons of a similar, or, as it might, perhaps, be 
 more accurate to say, converse kind, why a pyramid 
 which poises on one of its tips has no stability of 
 attitude, but topples over on its side on the slightest 
 provocation. When it is thus insecurely balanced, 
 with a disposition and destiny, if it rocks at all, to fall 
 irretrievably, it is said to be in a position of " unstable 
 equilibrium." 
 
 Our examination of the conditions on which the 
 stability of a pyramid depends has incidentally rendered 
 us able to discern at a glance why an overloaded 
 waggon will upset on a bit of road slanting sharply 
 towards the ditch on either side, which it would traverse 
 without risk or disaster if it were empty. And there 
 can be noone who has gone along with what has been 
 already said who must not fully understand why an 
 egg is contented enough to lie lazily on its side, but 
 cannot be made to stand in what may be called an up- 
 right attitude. You recollect the old story of Columbus 
 and the egg. Some bets were made at a party at 
 which Columbus was present that he could not make 
 an egg keep erect on either of its extremities. He cut 
 
children's toys. 
 
 73 
 
 the knot of the difficulty as summarily as, according to 
 the story alluded to by the phrase which has been just 
 this moment used, Alexander the Great did the Gordian 
 Knot with a slash of his sword, by dabbing the egg 
 down on the table so as to stave in one of its ends. 
 He thus supplied it with a broad base on which it could 
 steady itself. This solution of the problem was unsatis- 
 factory, inasmuch as the egg did not after all stand 
 on its end since it had none left for the purpose. 
 
 We can do something which is akin to the egg-feat, 
 which will bring out into clear view the precise nature of 
 the difficulty which has to be encountered, and the only 
 plan in which it can be met, if we balance a soda-water 
 bottle on one of its ends. The general appearance of 
 
 such a bottle is suggestive of a great glass egg. It 
 will not stand on its oval point, but will keep erect 
 on its other extremity, because a perpendicular line 
 drawn from its centre of gravity, which is at about the 
 middle of its stomach, falls within the limits of the 
 circular base which is afforded by its mouth. 
 
 In many of our habitual bodily gestures we uncon- 
 sciously, and automatically, supply illustrative demon- 
 
74 
 
 children's toys. 
 
 strations of the fact that a posture of stable equilibrium 
 is intrinsically adverse to motion, while one of unstable 
 equilibrium is essentially favourable to it. For example, 
 how does a m an who is intending to walk across the room 
 dispose himself, in preparation for that enterprise ? Does 
 he set his legs as if they were the two limbs of the letter 
 V turned upside down, that is to say, pyramidically, 
 with his body so poised above them as that his centre 
 of gravity, which is probably somewhere within the 
 course of a straight line drawn horizontally from about 
 the middle button of his waistcoat to the small of his 
 back, shall be supported by them in a position of stable 
 immobility, in which it will desire to remain comfortably 
 quiescent, and from which it cannot readily be dis- 
 lodged ? 
 
 By no means. He begins by leaning forwards, 
 thus throwing his centre of gravity in front of, so that 
 it is therefore no longer perpendicularly over, the base 
 which is constituted by his feet. He thus brings his 
 body into a state of unstable equilibrium which would 
 cause it to topple over, were not a fresh base imme- 
 diately supplied by the putting of a leg forwards. 
 That the position before the moment when the leg is 
 thus advanced is one of unstable equilibrium may be 
 readily ascertained by suspending further progress 
 when the attitude of leaning forward, which is prepara 
 tory to motion, has been assumed, and before the step 
 which should succeed this action has been taken. It 
 will be found that the posture of the body at the juncture 
 in question is such an one as cannot be maintained 
 without some exertion to prevent falling. 
 
 Assuming, however, a step to have been taken in the 
 
children's toys. 
 
 75 
 
 usual manner, this is only introductory to the assumption 
 of a fresh condition of unstable equilibrium by which, 
 the subsequent advance of the leg which is behind will 
 be necessitated. Walking is thus seen to be in fact a 
 continued series of small feats in balancing, for the ac- 
 complishment whereof the performer's original condi- 
 tion of stable equilibrium is purposely and unavoidably 
 abandoned for a transient state of an opposite kind which 
 is such as to be preparatory to motion. The tendency 
 to fall which is thus induced is instantly corrected, as 
 often as it occurs, by a momentary resumption of an at- 
 titude of stability, to be immediately afterwards ex- 
 changed for the instability which is indispensable as a 
 prelude to fresh progress. 
 
 A rapid alternation, such as has been described, of 
 gestures accurately adjusted to the purpose which they 
 are to promote, and their efficient achievement, demands 
 an adroitness which, although it is in the first instance 
 acquired, like one's native language, by insensible de- 
 grees, and is gradually brought to perfection by habit 
 so that at last it is automatically exercised, is none the 
 less a real feat in gymnastics, the capacity for which 
 is more or less suspended or destroyed when the brain 
 of the performer, through drinking, or any other cause, 
 has lost its cunning. 
 
 It is due to Dame Nature not to part from the sub- 
 ject of walking without gratefully acknowledging the 
 provision which she has made for saving us unnecessary 
 exertion by giving us bends at our knees. A little ex- 
 amination of the matter will show that it is owing to this 
 contrivance that the advance of our centre of gravity, 
 when we walk, is by a softly undulating line. Were the 
 
76 
 
 children's toys. 
 
 knees stiff, the centre of gravity would have to be 
 raised higher at each step than is necessary when the 
 joints in question are flexible, so as to allow the foot to 
 clear the ground ; for to brandish the leg round with a 
 semicircular sweep, which would be the only other alter- 
 native, would be still more inconvenient. That this would 
 be so may be visibly demonstrated by walking a cheap 
 doll, whose anatomy is too incompletely developed to in- 
 clude practicable knees, across a table. The line of pro- 
 gress of the centre of gravity of a man similarly con- 
 ditioned to such a doll, through having stiffened joints, 
 or from having lost his legs to above the knees, must be, 
 as will be found, a series of arches, so that his gait will 
 be less flowing, and far more laboured, than it would be 
 if the usual facilities for walking were available to him. 
 
 The principles on which our tumbler, who gave 
 occasion to this long disquisition on gravity, conducts 
 himself, have long since, as it may be hoped, become 
 sufficiently manifest. His figure is made of light 
 materials, and a concealed weight is introduced near 
 its base in such a manner as to bring his centre of 
 gravity to some point very near the lowest part of his 
 person. The figure being so prepared and trimmed, 
 recovers itself, after it has been caused to rock to 
 either side, precisely as a pyramid does when tilted as 
 just now described, and for reasons which have been 
 already enlarged upon. A boat, of course, is ballasted 
 on just the same principle. A tumbler, if he were set 
 to stand upon his head, would really act up to his title, 
 and do nothing but tumble, for the same reason that 
 an egg will not stand on its end, or a teetotum, when 
 at rest, on its peg. He would have the unstable 
 
childken's toys. 
 
 77 
 
 equilibrium of a man perching on one wooden leg, or 
 on a single stilt. 
 
 If a teetotum be so constructed as to have its 
 centre of gravity below the point of the peg on which 
 it spins, it will then stand erect, even when at rest. 
 This can easily be proved by experiment. Any bit 
 of cork, or other convenient substance, may be made 
 into a teetotum by simply sticking a pin through 
 the exact middle of its mass. Of course it will not 
 keep upright of its own accord as it is now, but its 
 disposition in this respect may be altered by the 
 addition to it of weights suitably adjusted for the pur- 
 pose. Such adjuncts will readily be furnished by two 
 
 forks stuck into the cork on opposite sides of it in 
 such a manner as to make with one another an angle 
 like that which is formed by the legs of a pair of com- 
 passes when a little opened. The teetotum will now 
 be found to balance securely if it be set to poise with 
 its pin resting on a stick or on any other support 
 which will allow the forks to swing as they please 
 without touching anything. The secret of its newly 
 
78 
 
 childeen's toys. 
 
 acquired faculty of maintaining its equilibrium is that 
 the centre of gravity of the cork and forks taken to- 
 gether, and constituting, as they in effect do, one 
 figure, now falls at a spot which is 
 lower than the point of the pin. 
 
 Here is a more ornamental example 
 of the same principle in the shape of 
 a common toy in which a dancing lady 
 pirouettes on the tip of one toe, through 
 the aid of bullets attached to her waist 
 by stiff rods, so that her centre of gra- 
 vity when she is thus accoutred is below 
 her feet. It is no less easy to construct 
 a top which will stand upright, although 
 stock still, upon its peg, as will be 
 shown bye and bye. 
 
 A rocking-horse, when at rest, maintains its upright 
 position for the same reason, speaking generally, that 
 the tumbler does. There is no rocking-horse among the 
 
 collection of things which is before you, because it is 
 rather a cumbrous thing to take about, and we do not 
 particularly want it, but here is what looks like a rock- 
 
children's toys. 
 
 79 
 
 ing-pony. It is, as you see, a sort of hybrid article, par- 
 taking about equally of the character of a rocking-horse 
 and of that of a tumbler. My reason for presenting it 
 to you is that it aptly introduces the topic of weighing 
 by scales, as to which I wish to say something. Scales 
 are very popular as toys, for I notice that bushels of 
 them are sold in the Lowther Arcade at a penny apiece 
 and upwards, and they are therefore entitled to notice 
 this evening. The connection between this toy and a 
 pair of scales is not, perhaps, at this moment, self- 
 evident, but it will reveal itself in the fulness of time 
 a few minutes hence. 
 
 As introductory to the subject of scales, the 
 question must be asked, " What is weight ? " A true 
 answer to that inquiry will now be readily forthcoming 
 on your part, and will be of this kind. The weight of 
 anything is the force which it exerts in endeavouring 
 to get towards the centre of the earth. This endeavour 
 represents, and is the accurate expression, both in its 
 direction and in its energy, of the attraction which the 
 earth, by means of its gravity, exercises on the body 
 in question. The body would go on moving, as we 
 know, towards the centre of the earth without ever 
 stopping until it reached that goal, unless its progress 
 were arrested by some means or other. We cannot 
 easily pronounce with what exact degree of force it 
 moves unless and until we stop it, but if we interrupt 
 its march by interposing some obstacle which it has, if 
 possible, to overcome, we can appraise the power which 
 it exercises in the attempt to do so. This may be done 
 in many ways, but the most common and convenient 
 method is by the familiar agency of a pair of scales. - 
 
80 
 
 children's toys. 
 
 Plere is a paper containing sngar. I hold it up 
 in my hand. It is attracted towards the centre of 
 the earth, but makes no movement in that direction 
 simply because I don't just yet permit, it to start. I 
 now release it from the durance of my fingers. It is 
 instantly obliged by the compulsion which the earth 
 employs to set forth, or, as the proceeding is commonly 
 termed, falls. 
 
 Now let me just this once more, and it shall be for 
 the last time, beg you to beware of the confusing error 
 which many people, in spite of repeated warnings, allow 
 to retain a grip on their understandings, that anything 
 falls of itself. Nothing originates its own motion a 
 bit more than a wooden leg goes oat walking of itself, 
 and a pound of sugar is no more likely, through any 
 internal capability and will of its own, to hurry from 
 my hand to the floor, than it is to get up and dance a 
 jig. It is strange that a fact which one would have 
 thought was self-evident, namely, that everything is and 
 must be passive, and that nothing but force originates 
 motion, should have ever required demonstration. It 
 was not, however, clearly realized and accepted until 
 Kepler won for it the position of a familiar truth. 
 
 Now the earth attracts bodies with a force which is 
 exactly proportionate to their mass, that is to say to the 
 quantity of matter which they contain, so that objects 
 which have more substance in them are attracted with a 
 correspondingly stronger power than those which have 
 less, or in other words, the former are, as it is familiarly 
 expressed, heavier than the latter. 
 
 Here is a second packet of sugar containing twice the 
 quantity of that in the first paper. It'strives to go to the 
 
children's toys. 
 
 81 
 
 ground, that is to say, as far as it can get towards the 
 centre of the earth, with a force twice as great as that by 
 which the first packet was animated, because it contains 
 double the quantity of matter. If the parcels were to be 
 allowed to fall upon the floor, it would be very difficult 
 indeed to form even an approximate estimate of their 
 comparative or respective weights, but we can appraise 
 these with complete ease and accuracy by interposing 
 in the path which each of them pursues when released 
 from the hand one of the saucers of a pair of scales. 
 
 Any downward pressure exerted by the packet of 
 sugar will now be spent upon the saucer beneath it. Into 
 the other saucer we put some substance whose mass 
 will evoke from the earth's gravity a certain quantity 
 of attracting force the amount of which has been ascer- 
 tained, and which we call by some distinctive name 
 indicating its precise value in point of strength. This 
 criterion of the degree of attractive force we term a 
 weight. Such tests are usually made, for handiness, 
 of iron or lead, or at any rate of some metal or sub- 
 stance which may be readily so fabricated as to contain 
 any prescribed mass of matter in an exact and compen- 
 dious form. We add to, or take from, the freight of one 
 saucer or the other as may be most convenient, until the 
 two loads balance one another in downward pressure so 
 that equilibrium becomes established. In the case of 
 a lb. weight, the block of iron which is used acts with 
 the particular degree of force which people have agreed 
 to call a pound. If it exactly balances the sugar, the 
 latter is said to weigh a pound. The real nature of the 
 proceeding in so extremely simple a matter as the 
 weighing oat of apound'of sugar appears to be, demands, 
 
 Q 
 
82 
 
 childeen's toys. 
 
 as you can now see, some little examination before it is 
 thoroughly understood. 
 
 The mechanism, too, of a pair of scales invites 
 consideration. The beam whence the saucers are 
 suspended, to prove satisfactory in use, should possess 
 three main good qualities. It should be strong; it 
 should be long; and it should be light. It should be 
 strong, because it is in an analogous position to that 
 of a stick which a man strains over his knee for the 
 purpose of breaking it. The weights in the saucers 
 represent, in the tendency of their action, the pulls 
 exerted by the man's arms, and the fixed point at 
 which the beam is supported corresponds, under the 
 circumstances, with his knee. But if the beam were to 
 bend, as it would do, when dealing with heavy weights, I 
 if it were not strong, this would disorganize the whole 
 process of weighing, and would vitiate the accuracy of 
 the indications given. The machine will be more lively 
 and sensitive if its beam is tolerably long and light 
 for mechanical reasons, which, as being concerned 
 with the elementary principles of the lever, are not far 
 to seek. Lightness, however, is not an easy quality to 
 preserve in association with the inflexible stiffness 
 which, as has been said, can by no means be dispensed 
 with. Aluminium, one would think, would be a good 
 material for scale-beams, as it is in a marked degree both 
 light and rigid. 
 
 A common method of combining as far as possible 
 the three elements of efficiency which have been men- 
 tioned is by the employment of abeam of an attenuated 
 oval shape like that of an almond. A beam of this kind 
 is frequently to be seen suspended from its upper 
 
children's toys. 
 
 83 
 
 surface,, or from a pin passing through a hole just under 
 that surface, at a point immediately above the middle 
 of its length. Since it is of a perfectly regular and 
 
 symmetrical form, its centre of gravity will be at the 
 centre of its mass, that is to say, at the middle point of 
 its length, and also at that of its depth between its 
 upper and under surfaces. For the sake of simplicity, 
 it will be as well to regard the beam as extremely thin, 
 and treat it as if it were merely a surface without any 
 depth at all, which, for all present purposes, may be done 
 without error. Every such beam is in fact made as thin 
 as is compatible with the maintenance of an unyielding 
 firmness of structure, in order that it may be as light, 
 and consequently as sensitive, as possible. 
 
 Now the centre of gravity having the situation 
 which has been already pointed out, does not coincide 
 with either of the spots at which, as has also been 
 observed, the pivot on which the beam swings, or the 
 
84 
 
 children's tots. 
 
 attachment whence it hangs, are often placed. The action 
 of a pair of scales whose beam is so swung as has just 
 been described is necessarily faulty. You will readily 
 see that this must be so. Make this horse prance by 
 raising or depressing for a moment either end of the 
 crescent- shaped frame on which he stands. As soon as 
 the effect of the temporary rocking motion which has 
 been caused is worn out, he regains a settled composure 
 by reverting to his original position, which is the only 
 one in which, when quit of disturbing constraint, he 
 will acquiesce. 
 
 The governing principle of his conduct in so doing 
 is transparent. For consider him as he is when at rest. 
 Here (see page 78) is the point on which, when quit of 
 all external influences, except that of his own gravity, 
 he reposes. His centre of gravity must therefore be in 
 a perpendicular line above this point. Now when you 
 make him rear or kick, you, as an obvious consequence, 
 which will manifest itself on experiment, throw his 
 centre of gravity to the right or left, as the case may 
 be, of the perpendicular line drawn upwards from his 
 point of support on the floor or table. The result of so 
 doing will be to incite the force of gravity, as soon as 
 it regains free play, to reinstate the figure in its first 
 posture. It is the old, and now wearisome, story of 
 the pyramid and of the tumbler over again. Far be 
 it from me, therefore, to enlarge upon it anew. 
 
 The beam of an oval scale, unless it be hung from its 
 centre of gravity, is, as you see, by its innate disposition, 
 and in its real effect, a tumbler. But in case this should 
 not be quite plain to everybody at the first onset I 
 interposed the rocking-horse between the two, since he 
 
children's toys. 
 
 85 
 
 is half-brother to both, resembling each of them to 
 some extent in respect of the gravitating qualities of 
 the frame on which he works, so that when the transi- 
 tion is made from one to the other through him, he 
 does something towards taming down any violence 
 which might otherwise be thought to exist in the re- 
 presentation that the tumbler, the pyramid, and the 
 scale of the beam are, mechanically speaking, a triplet 
 of twins. 
 
 We have not yet, perhaps, followed out as com- 
 pletely as we ought to do, the inquiry why the action 
 of a pair of scales whose beam does not swing on its 
 centre of gravity must of necessity be faulty. The 
 question is not so abtruse as that it would require the 
 ingenuity of a Queen of Sheba to propound it, or the 
 acumen of a Solomon to give the answer. Imagine 
 the saucers of a pair of scales, hung from a beam which 
 swings as has just been supposed, to be loaded with 
 unequal weights, so that one rises, and the other 
 descends. The beam therefore assumes a slanting 
 • instead of a horizontal position. It has been compelled 
 to accept a change of attitude, but while so doing it 
 has exerted a continued and increasing resistance to 
 motion on its own account. Its disposition, mechan- 
 ically speaking, is like that of the impracticable people 
 who oppose the inertia of their own heavy stolidity to 
 progress, however legitimate, in any direction, simply 
 on the ground of its being progress. 
 
 Now a pair of scales, emblematic as it is of Justice, 
 should, in consonance with the first essential principle 
 of judicial impartiality, be free from any partisan spirit, 
 and behave as a mere passive registrar of the fact of the 
 
86 
 
 children's toys. 
 
 equality, or of the precise degree of the preponderance, 
 of one or the other of the two forces whose mutual re- 
 lations to one another it is to determine and display. 
 It should wholly and exclusively surrender itself, with a 
 completely passive " abandon," to the natural influence 
 of the weights with which it is concerned. But in this 
 case the beam, literally speaking, throws something of 
 its own weight into the scale. For the rise of one 
 saucer, and the fall of the other, are both equally 
 discouraged and impeded, and the difference in the 
 weights of their respective loads, which it is the par- 
 ticular duty of the instrument to determine, is to some 
 extent falsified. 
 
 In rough measurements of heavy goods, where slight 
 inaccuracies are not material, the error introduced by 
 the personal proclivities of a beam not revolving round 
 an axis passing through its centre of gravity may be 
 disregarded as immaterial, but if the same instrument 
 were to be employed for appraising small modicums 
 of delicate substances, such as a chemist deals with, the 
 misrepresentations of weights might become of serious 
 consequence. 
 
 The nature of the perversion of truth which, albeit 
 small, would really occur, may be caused to reveal itself 
 by means of a scale-beam designedly so formed as to 
 magnify the error into proportions large enough to be 
 readily visible. Here is a pair of scales with a beam 
 which is of a purposely exaggerated breadth; it is, 
 indeed, square. Anyone who may have occasion to 
 take some medicine of so active a character that it is 
 only to be used in minute doses, carefully limited, had 
 better not have it weighed out with a pair of scales like 
 
children's toys. 
 
 87 
 
 this. I will first of all, as you see, put a drachm weight 
 into one of the saucers of a pair of banker's scales, 
 which are of necessity truthful in their indications, and 
 I put enough of a white powder, which you are invited 
 to imagine is a powerful drug, into the other saucer, 
 and, as you observe, they balance. I transfer both of 
 these to the other scales, and you can now, as you see, 
 add some further quantity of powder without being 
 cautioned by any note of warning given by the beam, 
 that you have got more than the single drachm which 
 you suppose. If you pivot the beam on a peg at its 
 centre of gravity, upon which it can turn with freedom, 
 it will become healthily sensitive, and its judgments 
 will be pronounced with unalloyed good faith. 
 
 Now to make something like a clean sweep of the 
 subject of scales, while we have got our hands in for 
 manipulating the problem of the various conditions 
 which produce equilibrium, it may be as well to advert 
 to one remaining possible state of circumstances not 
 hitherto dealt with, which is that of a beam at rest, 
 but not in a horizontal posture. It may assume this 
 attitude either from swinging from a point to the right 
 or left of the middle of its weight, or from having one 
 of its saucers freighted more heavily than the other. 
 Can you bring such a beam to a state of horizontal 
 equilibrium by adding a weight to the side which is 
 already the heavier ? This would appear to be a 
 mechanical paradox, corresponding with a moral one 
 which may be put as follows : If a man has formed a 
 determination to do some particular thing, can you by 
 making that resolution stronger still, induce him to act 
 in direct contrariety to it ? Such an attempt would 
 
88 
 
 children's toys. 
 
 not seem to promise well. But one of the commonest 
 and simplest of all toys, which we may notice here, 
 discloses a clue to the problem, and shows that there 
 may be more to discern even in a child's plaything 
 than negligent eyes are apt to observe. 
 
 Before you is a wooden ship. Its centre of gravity 
 is at about the middle of its hull. If you set it to rock 
 at the edge of the table, or on this stand, resting it on 
 the pegs which project from the hinder part of the keel, 
 its centre of gravity which does not come perpendicu- 
 larly over its point of support, being unsustained, 
 instantly makes its way downwards, and the vessel 
 comes to grief upon the floor. But take this bent wire 
 with a bullet at its end, and fix it towards the front of 
 the ship on the side towards which there is already so 
 strong a tendency to fall, and, oddly enough, as it seems, 
 
children's toys. 
 
 89 
 
 the added weight, instead of aiding and abetting that 
 inclination, is found to counteract it. The ship now 
 rocks in perfect security, having an equilibrium which 
 is indomitably stable, since however much and often 
 this may be transiently vanquished by some extraneous 
 agency, it never fails to reassert itself as soon as cir- 
 cumstances permit. 
 
 The explanation of the phenomenon is almost trans- 
 parent. The centre of gravity of the vessel, apart from 
 the weight, is, according to our supposition, somewhere 
 amidships. But when I feign to add a weight to the 
 side which is already the heavier, you must remember 
 that as far as relates to the conditions of balance, the 
 ship, with the appendage which is fastened to it, con- 
 stitutes in effect but one figure : and you will observe 
 that the curve of the wire is so adjusted as to bring the 
 centre of gravity of the whole affair underneath its point 
 of support. The real truth is thus arrived at, that al- 
 though a pretence is made of supplying a further weight 
 to one side it is in reality bestowed upon the other. 
 
 The seeming physical inconsistency of causing 
 equilibrium to be gained by ostensibly strengthening 
 the conditions which are most opposed to it is also 
 illustrated by an old familiar trick, which is given in 
 most of the common children's books of games and 
 pastimes, such as the " Boy's Own Book/' and " Par- 
 lour Magic," &c, and is done as follows. A bucket of 
 water is suspended from the end of the free portion of 
 a stick which partly rests upon a table and projects for 
 some distance over the edge. The stick not being fixed 
 or propped in any way, the bucket to all appearance 
 hangs from no adequate support. 
 
90 
 
 children's toys. 
 
 The illusion is created by trigging a second stick 
 against a notch in the first one, and also against the 
 bucket, and so disposing it as that it thrusts the latter 
 
 nearly altogether under the table. The bucket cannot 
 now fall, because the first stick, as may be observed, 
 can neither slide along its surface length, nor turn over 
 at the edge of the table, as on a hinge, without raising 
 the centre of gravity of the bucket. Under the circum- 
 stances, therefore, which have been brought about, the 
 weight of the bucket is enlisted in the cause of resist- 
 ance to motion instead of in that of producing it, so 
 that the whole situation is one of immobility. 
 
 We have talked about the attraction which the 
 Earth exercises by its gravity, and we have also dis- 
 cussed the method in which, by means of scales, the 
 power of this force may in many cases be estimated. 
 Now with reference to these topics, suppose that some 
 troublesome person like the inquisitive little Caffre 
 boy who has attained a conspicuous place in history 
 by his perplexing questions to Bishop Colenso were to 
 ask you whether the weight of the Earth can be ascer- 
 tained and if so what it would be, how would you answer? 
 
childeen's toys. 
 
 91 
 
 There are probably some people who might reply 
 that the Earth cannot possibly be weighed, for that no 
 tackle conld be got to do it. They would say that 
 such an operation would be in more senses than one 
 on too large a scale. They would add that the un- 
 known weight, whatever it may amount to, must reach 
 a high figure, because let alone the hidden contents of 
 the inside of the globe, which are probably substantial 
 enough, there are so many ponderous objects on its 
 surface. So that although the precise weight of the 
 whole concern may not be within reach of even a con- 
 jectural estimate, it certainly is not quite the sort of 
 thing which one would like to have dropped on a 
 tender toe. 
 
 Now the first of these answers, namely, that the 
 Earth cannot be weighed, is wrong. The tackle re- 
 quired for the operation exists. Scales are not by any 
 means the only instruments for estimating weight. 
 The same purpose is answered by an elastic metal 
 spring, which indicates by its degree of collapse the 
 precise amount of any weight by which it is depressed. 
 The Steelyard, again, although it may be viewed as 
 only a modified form of a pair of scales, is not precisely 
 the same thing. Mercurial and aneroid barometers 
 are also mere weighing machines. In the case of the 
 former of these instruments the indications of weight 
 are given by the height, from -time to time, of a column 
 of mercury which is supported by the pressure of the 
 atmosphere, that is to say, by the weight of the air. 
 The aneroid barometer furnishes the desired test by 
 means of a collapsible metal box kept partially ex- 
 panded by a steel spring. The strength of the effort 
 
92 
 
 children's toys. 
 
 which the atmospheric pressure is able to put forth in 
 squeezing the box against the opposition of the spring 
 is made to show itself upon an index. 
 
 Another device for weighing may be adverted to. 
 It is often requisite, for the purpose of ascertaining the 
 quality or character of some given liquid to determine 
 its specific gravity, that is to say its heaviness, as 
 compared, bulk for bulk, with a particular standard; 
 namely, that of distilled water. This object is accom- 
 plished by plunging into the liquid a hollow tube 
 marked along its length with a graduated scale, and 
 equipped with a sufficient weight at one end to cause 
 it to swim in an upright position like a float used in 
 fishing. The greater or less depth to which the in- 
 strument immerses itself forms a gauge, through a 
 principle which we have no time to discuss here, of 
 the specific gravity, or precise weightiness, of the 
 liquid. The usual process of weighing is in this 
 case apparently reversed, since the scales are, as it 
 were, put into the liquid, instead of the liquid into 
 the scales. 
 
 There are many other means of weighing besides 
 the familiar ones of which I have just reminded you, 
 such as, for example, that which is grounded on observ- 
 ation of the time occupied by the swing of a pendu- 
 lum ; which process, though mentioned last, is perhaps 
 the most important of aj.1, as it is one of the methods 
 by which we are enabled to determine the gravity of 
 the world. 
 
 Sir Isaac Newton calculated the weight of our 
 globe, and not of it only, but of many other stars also. 
 If you look at his monument next time that you go 
 
children's toys. 
 
 93 
 
 into Westminster Abbey, you will see that his feat of 
 solving these problems is there commemorated by an 
 allegorical scene, carved in white marble, in which 
 little cherubs are represented as engaged in weighing 
 the stars with steelyards. The faculty of weighing the 
 stars is of as much consequence to an astronomer in 
 the pursuit of his vocation as the use of scales is to a 
 grocer. It may be added that the operations of the 
 natural philosopher in this, as in a thousand other 
 particulars, not only extend the limits of general 
 knowledge in various directions, but if the truth were 
 known, have, in many cases, nearly as close and ma- 
 terial a bearing on our everyday interests and necessi- 
 ties as the proceedings of the worthies who supply us 
 with tea and sugar. 
 
 As to the second question which was proposed just 
 now, namely, " What does the Earth weigh ? 99 the 
 answer, in one sense, is "nothing." For we have 
 seen that the weight of anything means the force with 
 which it is attracted towards the centre of the Earth. 
 If this definition were to be taken as holding good for 
 all circumstances, the Earth could not be said to weigh 
 anything at all, since it cannot, of course, attract itself. 
 But it attracts other heavenly bodies, and in this sense 
 its weight is considerable. The number of tons at which 
 it would scale has been computed, and is represented, 
 when given arithmetically, by a long train of figures. 
 Human faculties of conception are soon defeated when 
 they encounter large magnitudes, so that a numerical 
 statement in the present case would convey no real 
 meaning to your minds. It would be but an expression, 
 bewildering perhaps, but void of import for our finite 
 
9i 
 
 children's toys. 
 
 powers of apprehension. Nor is any one but an as- 
 tronomer concerned to know what the precise amount 
 of the weight in question is. But we are all vitally- 
 interested in the maintenance of the exact status quo 
 of the gravity, whatever it may be, of our Earth. For 
 were it to increase or diminish in the smallest degree, 
 the balance of the forces which keep the mechanism of 
 the universe in motion, and preserve the exquisite 
 smoothness and precision of its working, would be 
 instantly upset, and there would be a general crash 
 and ruin throughout Creation. Such an occurrence 
 would prove a source of discomposure and annoyance 
 to many persons, and would cause an inconvenient dis- 
 location of arrangements. 
 
 The law which regulates the effect of gravity has 
 been already mentioned, but it may be as well to recall 
 it. Stated in very general terms it is as follows. The 
 force which the attraction of gravity exerts is in direct 
 proportion to the mass of the attracting body and to 
 its nearness to the body which is attracted. Both the 
 two characteristics which have just been stated as 
 marking the action of gravity may be more fully enun- 
 ciated in the following manner. Every particle of 
 matter attracts and is attracted by every other particle 
 of matter with a force inversely proportioned to the 
 squares of their distances from one another. Hence 
 you see (to take something very familiar as an illustra- 
 tion) it follows that a pound of tea taken up in a balloon 
 must become lighter and lighter as it gets farther from 
 the Earth, the attraction of the latter upon it becom- 
 ing feebler and feebler with the length of the distance 
 through which it operates. 
 
children's toys. 
 
 95 
 
 An estimate of the attraction which is exercised by 
 the Earth's gravity at any given distance from the 
 surface of the globe may be very easily made, because 
 its power, at that surface, can be roughly appraised 
 in a moment by actual and simple experiment. Hence 
 we readily get a fair starting-point for calculation. The 
 force which the Earth's gravity exerts, say, at this spot 
 where we are assembled, if it were to be tested by a 
 well-known apparatus, called "Attwood's machine," 
 would be found to be just sufficient to draw any and 
 every object, of whatever kind it may be, through a 
 space of 15 feet in one second. 
 
 This power is curtailed in practice by the resist- 
 ance of the air, which varies with the form and 
 constitution of every object which is exposed to its 
 action. If the multitude of tiny atoms which in the 
 aggregate constitute the substance of any given object 
 are closely packed, the gravitating power of the whole 
 body, being, as it is, nothing more nor less than the 
 sum of the impulses by which the particles which com- 
 pose the mass are animated, becomes condensed, in 
 effect, into a small focus, and only a correspondingly 
 limited surface is afforded upon which the resistance 
 of the air can operate. A furled umbrella would drop 
 more quickly than if it were extended parachute - 
 fashion, and the Times, if squeezed up into a paper 
 ball, would make an earlier arrival at the floor than it 
 would do if it were to be let fall as an expanded sheet. 
 The Earth's power, therefore, of occasioning by its 
 gravity a movement of 15 feet in a second, at its 
 surface, is to be taken to mean a capability of pro- 
 ducing this effect in vacuo, that is to say in a field of 
 
95 
 
 children's toys. 
 
 action from wliicli tlie air with, its retarding influence 
 has been excluded. 
 
 Now the point whence the Earth's attraction is 
 exercised may be taken, as we have seen, to be its 
 centre of gravity, which in this particular case is 
 as nearly as possible coincident with the middle of its 
 figure. This central point, the innermost recess of 
 the core of the big orange on which we live, is, as 
 you know, somewhere about 4,000 miles from each 
 and every point on the surface of the globe. The 
 attractive power of the Earth's gravity amounts, as 
 hence appears, to a force endued with sufficient vigour 
 to pull any of the objects which are about us, or our- 
 selves, whether slim or corpulent, through a distance 
 of 15 feet in one second. In other words, such is the 
 measure of its strength when acting at the distance 
 which has been mentioned from its seat of power. 
 
 I have not dwelt thus persistently upon the subject 
 of gravity without abundant justification, or, indeed, 
 without clear necessity, since anyone who did not 
 know something of the mode in which the force in 
 question acts could not possibly understand even such 
 simple affairs as the toys which we have lately passed 
 under review, or a single one of ten thousand things 
 which constantly surround us in our every- day life ; 
 much less, of course, could even the most elementary 
 conception be acquired of the first rudiments of as- 
 tronomy, of which everybody of intelligence should 
 have at least some idea. 
 
 In concluding this subject, let me beg you to notice 
 the particular language which was designedly employed 
 when it was said that you should understand ce some- 
 
children's toys. 
 
 97 
 
 thing of the mode in which gravity acts." We can 
 note and estimate the effect which the attraction of 
 gravity produces, but what the force is in itself, or, 
 indeed, for the matter of that, what any force is, are 
 secrets which no man living can reveal to you. It was 
 stated at the outset of this lecture that any examination 
 of even the humblest toys leads straight up to some of 
 the highest and most difficult problems in natural 
 philosophy : we have in this tumbler a proof of that 
 assertion. Any of you who can reveal to the world 
 what gravity is will instantly take rank with Newton, * 
 and the greatest philosophers who have ever lived* If, 
 therefore, you desire to make a short cut to a glorious 
 immortality of fame, an eligible opportunity for so 
 doing offers itself to anyone who will give a really 
 complete explanation of the toy before us. 
 
 Let me take this opportunity, while we pause for 
 a moment before making a transition to fresh ground, 
 of commending the judicious and agreeable practice of 
 introducing, as is sometimes done, a musical interlude 
 into the midst of a lecture. The tedium of the whole 
 proceeding is rendered a little less oppressive if its 
 continuity is thus broken. A dissertation on toys 
 would lend itself with exceptional aptitude to such an 
 arrangement, since the matters over which it ranges 
 form, as it were, but a loose confederation of subjects 
 gathered, for the time being, under one titular head ; 
 and in traversing the series it is often found that 
 members of it which happen to stand next to one 
 another are in no necessary contiguity. The openings 
 thus afforded for intervals of relaxation seem to invite 
 
 H 
 
98 
 
 children's toys. 
 
 musical episodes as a relief from the monotony of the 
 speaker's voice. 
 
 On a recent occasion when a lecture was to be 
 given at a certain place in the country, the expediency 
 of imparting variety to the coming entertainment 
 was duly felt, but no local resources for the purpose 
 being available, a musical box was borrowed from a 
 neighbouring Parish. At the first favourable break 
 in the lecturer's discourse, the instrument was duly 
 wound up, and set going, but as it was, as has been 
 stated, a stranger in the Parish, a knowledge of the 
 proper manipulation of its arrangements had not been 
 acquired. The consequence was that it played " Cheer, 
 boys, cheer " over and over again, and nothing else, 
 and could not be stopped. This performance, after 
 it had continued for half an hour or so, was con- 
 sidered to partake of sameness; and all the welcome 
 symptoms of voluntary cessation which from time to 
 time appeared and were eagerly hailed, proving un- 
 happily to be merely preludes to renewed outbursts 
 of the same tune, given with fresh and fiendish energy, 
 the dreadful instrument was at length borne forth to 
 another room. There, in tones subdued by distance, 
 but still audible, it continued, with the same " damn- 
 able iteration, " to pour forth its one odious song 
 throughout the evening. 
 
CHAPTER IV. 
 
 E now come to a very large and interesting 
 class of toys which all work upon simple 
 mechanical principles. When you under- 
 stand their springs of conduct, you will 
 find that you also comprehend, perhaps for the first 
 time, or at any rate better, probably, than you ever 
 did before, the action of numerous implements and 
 machines which are constantly before your eyes, and 
 with whose services your convenience and enjoy- 
 ment of life is largely and intimately connected. The 
 toys in question are such, for example, as bats and 
 balls, shuttlecocks, kites, arrows, and flying tops. 
 Among the contrivances which ply their various tasks 
 under mechanical conditions which these toys, for the 
 purposes of comparison and necessary illustration, will 
 lead us to examine, are wiudmills and watermills, ships' 
 sails, the screws of screwsteamers, ventilators, smoke- 
 jacks, and others. 
 
 Now there is one, and only one, very simple and 
 elementary item of information which must be bought 
 at the price of a little attention before you can under- 
 
100 
 
 children's toys. 
 
 stand any mechanical toy or implement. When you 
 have once secured this, yon will find that you hold in 
 your hand the key to the comprehension of all sorts of 
 phenomena which are now locked up from your insight 
 in the dim cabinet of mystery. 
 
 Suppose you have a weight, like this, for example, 
 which is borrowed from the kitchen scales, and is very 
 convenient for our present purpose, as it is furnished 
 with a ring at the top whereto we can attach a string. 
 And suppose that you pull that string with sufficient 
 force to draw the weight, what happens ? The weight, 
 of course, has no alternative but to follow the string. 
 It does not require a Newton to establish that much. 
 But now suppose that you have two strings, and that 
 you pull both at the same time in some more or less 
 diverging, but not precisely opposite directions, what 
 does the weight do ? It cannot obey both, since to do 
 so would be to go two ways at once, so it follows 
 neither, but takes an intermediate course between 
 them. We are thus led towards a particular conclusion 
 which we may regard as a general law applicable to all 
 similar cases, and which will be best understood if it 
 be set forth in black and white by a diagram. 
 
 Suppose, then, a b [< ^ A to be a weight acted 
 
 upon by two differ- 
 
 were exerted just D 
 
 ent forces, such as 
 now by the strings, 
 
 one of which endeavours to draw it along the line a b, 
 and the other along the line AC. The weight can- 
 not comply with the solicitations of both these forces 
 at the same time, so, as we have already found by 
 actual experiment, it pursues an intervening track 
 
children's toys. 
 
 101 
 
 such as A r>. Can we discover what the exact length 
 and direction of a d will be ? We can, in the following 
 manner. 
 
 Suppose the two forces which are conceived as 
 acting upon A to be severally represented both in 
 power and direction by two lines such as A b and a c. 
 If the lines are to represent the forces properly, and 
 the forces are equal, then they must be drawn of 
 equal length, whatever that may be. If the forces 
 be not equal, then the lines must be so drawn as 
 that their mutual relation in respect of length shall 
 accurately reflect the comparative strengths of the 
 forces. Thus, suppose a b to be a force of 4 lbs, that 
 is to say of such a power as would suffice to support a 
 weight of 4 lbs, and prevent it from falling to the 
 ground ; or strong enough, when acting vertically, to 
 press down a scale with as much effect as if it were 
 itself a kitchen weight of that denomination. And 
 suppose a c to be a force of which a weight of 2 lbs 
 would similarly be the equivalent. Then, if we wish 
 to bring these forces from the regions of imaginative 
 conception down upon paper, so as to have them 
 represented in something like a visible personality, and 
 within conditions under which we can more readily 
 subject them to the judgment of our perceptions, we 
 may draw them on whatever scale may happen to be 
 the most convenient, provided only that their relative 
 powers and directions are faithfully symbolized in the 
 manner which has been prescribed. 
 
 In the present case, if a b and A c be the two forces, 
 and ab double AC, the line ab may be an inch, or a 
 yard, or a mile, or anything else in length, provided only 
 
102 
 
 childken's toys. 
 
 that it is twice A c. We have thus got a pair of lines 
 forming an angle B A or corner like 
 
 this. The acute- ness or obtuse* 
 
 ness of this angle, c that is to say its 
 
 degree of sharpness or bluntness of point, will be, of 
 course, a true exponent of the precise extent of diver- 
 gence of the forces which our diagram has brought 
 upon paper. Turn this open figure into a closed one 
 by drawing lines respectively parallel to ab and AC. 
 Then the oblong figure abcd is what is called a 
 " parallelogram." 
 
 " Parallelogram iy is rather a solid mouthful when 
 spoken, and has a formidable sound, as if it belonged 
 to some awkward and intractable puzzle which only a 
 mathematician could attempt to tackle. But its terrors, 
 like those of a scarecrow, are all in pretence, for it 
 is in reality the very simplest thing possible. A 
 parallelogram merely means a four-sided figure whose 
 opposite sides are parallel to one another. Under 
 this definition we may get four- sided figures of very 
 varied and multitudinous shapes. Squares, oblongs, 
 and diamonds on cards, are all examples of parallelo- 
 grams. Since any and every four-sided figure which we 
 can invent and draw will be a parallelogram, if only 
 its opposite sides be parallel to one another, the name 
 of such devices must be legion. To return to the 
 particular parallelogram with which we first started. 
 
 A line such as ad joining either pair of its opposite 
 corners is called a " diagonal." We now come to the 
 precise thing which is essential to remember, which is 
 as follows. If you have two forces represented by 
 
children's toys. 
 
 103 
 
 lines such as these ab and ac ; acting on a body at 
 A, and strong enough to move it, the body, as you 
 know, will not follow the direction of either force 
 exclusively, but will take an intermediate track. You 
 can predict exactly what this course will be by drawing 
 b d parallel to A c, and dc to a b, so as to complete 
 the parallelogram A b c d, and then linking the points 
 A and d by a line which will be a diagonal of this 
 parallelogram, and which will be found to be the track 
 which the body at a, when acted on by the forces A b 
 and AC, will actually follow. 
 
 We have now put two forces together, and seen the 
 result of so doing in what is called the composition or 
 putting together of forces. If you can put any two 
 given forces together, and exhibit the result of their 
 combination, you can manifestly pick any single one to 
 pieces, and show what its parentage either is, or may 
 be. Clearly this is so, but to make it doubly plain, let 
 us revert for one moment to our parallelogram of 
 forces. 
 
 Suppose any given line to represent the force which 
 you wish 10 dissect. Draw any parallelogram you please 
 which has this given line for its diagonal. Then the 
 line in question, as being that diagonal, will represent 
 the effect of either of the two pairs of forces which may 
 be respectively supposed to act at its opposite extrem- 
 ities, personated, as they each are, by two contiguous 
 sides of the parallelogram. Consequently, it is only to 
 put the same statement the other way up, or rather, in- 
 deed, simply to repeat it, to say that since the line is 
 equivalent to either couple of forces, they on their part 
 represent it just as much as it does them. 
 
104 
 
 children's toys. 
 
 We have thus, as you see, shown how to pick any 
 given force to pieces, and reveal what its parentage 
 is, or might be. Any force will be found, of course, 
 to be the possible offspring of innumerable other pairs 
 of forces, since parallelograms of endless multitudes of 
 shapes can be drawn. Each member, also, of these 
 pairs might similarly be referred to any number of 
 origins. 
 
 Having glanced at the main preliminary which 
 is of essential necessity to be understood before the 
 action of any forces can be investigated, we may 
 proceed to note its practical bearing on a variety of 
 things of every day life which may have appeared to be- 
 very simple, but which, as some of you will probably 
 come to admit, may be advantageously looked into 
 rather more closely than hitherto. 
 
 As a first illustration of this, suppose we. take a 
 windmill, as being one of the biggest, most prominent, 
 and most familiar features on the face of the country. 
 What makes the sails go round ? The answer, in one 
 sense, is not far to seek, namely, the wind. No doubt ; 
 but how does it produce its effect ? It can hardly be 
 said to blow the sails round, since its current is against 
 the plane in which they revolve, that is to say, at right 
 angles to the direction in which they move, so that it 
 actually contributes no direct propulsion at all. For 
 from whatever quarter the breeze may come, the mill, 
 as everybody knows, always turns its face flat and full 
 to it, as a sunflower does to the sun. 
 
 There is another circumstance which everybody who 
 has a pair of eyes must have noticed, and which would 
 of itself suffice to show that it is not the direct action 
 
children's toys. 
 
 105 
 
 of the wind which moves the sail. The fact in question 
 is that the sails often go round a good deal quicker 
 than the wind which is blowing on them is travelling. 
 One does not usually see a cart going faster than the 
 horse which draws it, and similarly, if the wind simply 
 twirled the sails by propelling them round their axle- 
 tree, it could not drive them at the rate of twenty 
 miles an hour while it was itself doing only ten. 
 
 What really takes place is far less simple. Although 
 the windmill faces the wind, the sails taken separately 
 do not stand flat towards it, but obliquely. We will 
 consider what the behaviour of any individual sail must 
 be under such circumstances, and whatever may be 
 found to be true for one will be no less so, of course, 
 for all. 
 
 If the sail be flat to the wind, the only tendency 
 which the latter can have with reference to it must 
 simply be to push it straight backwards, but not to 
 move it in any other direction. All the wildest and 
 most impetuous hurricanes which ever escaped from 
 the cave of iEolus might blow till they cracked their 
 
106 
 
 children's toys. 
 
 cheeks, but they neither could nor would impart to it 
 any motion at all unless it were to be that of bodily 
 transference from its existing situation to some spot 
 in its rear. They might succeed in tearing it, or in 
 upsetting the windmill, but they would not supply the 
 power to grind a single thimbleful of corn. 
 
 The sails, as has been already said, are severally set 
 obliquely to the wind, so that it strikes each of them 
 aslant. What comes of the encounter of the wind and 
 sail under these conditions ? Some idea of the answer 
 will be best worked out in the first instance on paper. 
 
 Suppose A b to be the sail with 
 its axle at a, and d c to repre- 
 sent the force of the wind striking 
 it, as the Americans say, slantin- 
 dicularly. What power has d c 
 to make A b turn round A ? To 
 possess any such capability d c 
 ^> must contain some ingredient in 
 its composition acting at a right angle upon A b which 
 will be in the direction f c. Let us pick the force d c 
 to pieces, and compel the particular element of which 
 we are in search to disclose itself, if it has any exist- 
 ence. We can do this in a moment by means of our 
 parallelogram of forces. The parallelogram to be 
 employed must, as you know, have the particular force 
 which we seek to dissect for its diagonal. With this 
 object we draw a line from c at right angles to A b, such 
 as c f, and then another line from c, such as c e, parallel 
 to A b. These lines may be drawn of any length, it does 
 not signify what, because they will be cut down to their 
 proper extent by the process of completing the parallelo- 
 
children's toys. 
 
 107 
 
 gram of which they are to form two of the sides. Com- 
 plete the figure accordingly, drawing from r> one line 
 parallel to c e, which will meet CP at a point which we 
 may call G, and another line parallel to c G meeting c e at 
 a point which may be marked as h. Then d g c h is a 
 parallelogram, and DC is a diagonal of it. The effect, 
 therefore, of a force represented by d c will be equiva- 
 lent to the joint action of two others such as are 
 impersonated by h c and a c. 
 
 Now a force such as h c could have no effect what- 
 ever upon A b. For h c was, as you remember, expressly 
 and designedly drawn parallel to a b, and a force 
 moving across, but not in any degree against, a flat 
 surface, which is the present case, can have no tendency 
 whatever to move it. As far as the miller's require- 
 ments are concerned, it must be quite valueless. The 
 force h c, therefore, may be disregarded, since with 
 reference to the actual conditions of the problem with 
 which we have to deal it is in fact a nonentity, and we 
 find ourselves landed on the conclusion that the effect 
 of dc upon A b is identically the same as that of G c. 
 You will observe that a stronger force when exerted 
 obliquely, as is the case here, has, as would naturally 
 be expected, no more potency for achieving any given 
 result than one which is weaker, but in the same pro- 
 portion more direct. We can determine in a moment 
 what the precise strength of the force gc is, because 
 we know what d c represents, and that G c bears the 
 same relation to whatever is thus symbolized as the 
 length of the line g c does to that of DC. The appraise- 
 ment therefore of the power of G c becomes a simple 
 matter of measurement. We thus, as you see, ascer- 
 
108 
 
 childeen's toys. 
 
 tain in a moment what we set ourselves just now to 
 elicit, namely, what effort a blast such as d b, blowing 
 obliquely upon a sail A B, would exert towards making 
 it revolve. 
 
 In introducing just now the question of what the 
 effect of the wind upon a sail set obliquely to it would 
 be, I used the expression that " some idea of the answer 
 may be made out on paper. " It was not by any means 
 meant that a complete and exact solution of the problem 
 could not be readily obtained by pen and paper. But 
 the actual computation would be too intricate a process 
 for a mixed assembly of people to go comfortably along 
 with, for the following reason. The length of a sail, of 
 course, might be accurately given, according to scale, 
 on the plane, that is to say on the surface, of the paper 
 on which it was drawn, and so could the breadth be, but 
 the direction of the wind would be necessarily perpen- 
 dicular to the face of the diagram, and could not, there- 
 fore, be represented at all on the same sheet, unless by 
 expedients which would unavoidably render the demon- 
 stration inconveniently complex. The sort of way in 
 which the precise action of the wind upon the sail may 
 be analyzed upon paper has been already indicated, so 
 that anyone who may care to do so should be able, 
 when at home and at leisure, to investigate the whole 
 business without further assistance than has now been 
 provided. 
 
 Now the principle of the windmill, that is to say the 
 contrivance whereby for all sorts of mechanical purposes 
 we convert the force of the wind, which of inherent 
 necessity must be exerted solely along the straight line 
 of its ow T n direction, into a source of circular movement 
 
childeen's toys. 
 
 109 
 
 at right angles to that course, is seen in operation in a 
 great multiplicity of examples. A windmill itself dis- 
 plays the principle in question as applied in two forms. 
 The sails are set and driven in the manner which has 
 been partially sketched, but behind them there is always 
 to be seen, as noone can have failed to notice, sometimes 
 aloft, and projecting outwards from the crown of the 
 building, and at other times surmounting a circular 
 travelling stage which runs on rails round its foot, what 
 looks like a juvenile windmill, and is called a " wind- 
 vane." Its office, as is easily discernible on observa- 
 tion, is that of turning the millcap, that is to say the 
 part of the structure which carries the sails, in such a 
 manner as to keep their faces to the wind, a duty which 
 it discharges by setting, as it revolves, certain cogged 
 wheels in motion. Its own adjustment is such that it 
 always presents its general figure edgewise to the 
 breeze, because in this position, besides actively work- 
 ing the apparatus with which it is connected by rotation 
 round its own axis, it also, by behaving as though it 
 were the vane of a weathercock, gains an increased 
 capacity for its duty of maintaining the sails in their 
 proper attitude. It is, as anyone may see, another 
 version of the very thing which, when playing a part in 
 a different sphere, is called a smokejack. 
 
 A smokejack is a windmill as well as a windvane, 
 but with shorter, broader, and more numerous sails, 
 which are employed for the following reason. If the 
 surroundings of the site where a windmill is to be placed 
 are such as to render a tall building admissible, it will be 
 expedient to build one of full stature, so that big sails 
 may be employed, since the longer these are, up to a 
 
110 
 
 childeen's toys. 
 
 certain point, the better. For instance, take any given 
 windmill to be furnished with 4 sails, and that each of 
 them is 30 feet long and but one foot broad. Then the 
 
 whole spread of sail computed in square feet will be 30 
 multiplied by 4, or 120 feet. Say that another wind- 
 mill is fitted with 6 sails, each 20 feet long, and 1 foot 
 broad. The whole extent of sail which this latter can 
 spread will be 20 multiplied by 6, or 120, that is to say, 
 the superficial area of canvas will be the same in both 
 cases. But the second mill will not have nearly so much 
 power as the first. For each sail is, mechanically speak- 
 ing, a lever, and a force, such as is in the case before 
 us the strength of the wind, when acting on a weight 
 here taking the form of the resistance on the part of the 
 axle which is to be turned, is exerted with proportion- 
 ately greater effect through a longer arm than through a 
 shorter one. " Long " and " strong " being convertible 
 terms when used of the arms of a lever in the sense 
 just referred to, 6 sails must possess less efficacy than 
 belongs to 4 in which latter a similar amount of wind- 
 catching surface is drawn out to a greater longitudinal 
 
children's toys. 
 
 Ill 
 
 extent. If, therefore, the height of a mill is, as is ex- 
 pressed in the vulgar tongue of the Servants' Hall, " no 
 object/' that is to say, if a high structure, which will 
 permit long sails to revolve clear of the ground, is 
 allowed by the conditions of the locality where it is to 
 stand, so much the better. 
 
 The length of the sails must still be kept within a 
 certain limit which is imposed on them by the strength 
 of materials and by other considerations which need 
 not be specified here. But there are, of course, many 
 circumstances under which it would be inconvenient or 
 impracticable to employ sails of full length, and in all 
 such cases their want of this dimension and consequent 
 lack of the efficiency which would have been derived 
 from more advantageous leverage, must be compensated 
 for, as far as possible, by increasing their number and 
 breadth. Hence the particular form of the windvane, 
 which is that also of the smokejack. 
 
 Smokejacks are rarely used nowadays, but they 
 were till lately so common that most people must have 
 seen such things. A working model of the main basis 
 of a smokejack may be roughly made in a few seconds 
 by slicing a circular disc of metal into several divisions 
 by cuts made from near the centre to the outside edge. 
 A small area in the middle is left untouched, whereby 
 the disc still keeps together as a whole, and which also 
 serves as a stage which is placed horizontally, and so 
 adjusted as to poise with an even balance upon the tip 
 of a pointed support, so that the whole disc on re- 
 ceiving any impulse is free to rotate with unrestricted 
 ease and freedom. Bach of the broad rays of metal 
 which have been formed by the divergent cuts is now 
 
112 
 
 children's toys. 
 
 bent a little, after the fashion of the sail of a windmill, 
 so as to present an oblique surface to a current of air 
 flowing against the face of the disc. The instrument 
 thus prepared is now supposed to be set in and across 
 a chimney. The draught upwards, formed by the 
 continuous ascent of hot air from the fire below, acts 
 like a blast upon the vanes of the sinokejack, and twists 
 them, and it, round. The motion hence generated is 
 utilized, through the intervention of suitable tackle, for 
 turning a spit. The throat of a chimney would not 
 admit of the employment of long sails, so that motive 
 power is obtained by an apparatus of more compendious 
 dimensions. 
 
 Similar considerations govern the construction of 
 the little spinning discs which are sometimes placed 
 over lamps to prevent the smoke from mounting in a 
 direct column, and thus blacking the ceiling. The 
 stream of hot air from the chimney of a lamp is strong, 
 but concentrated within a boundary which is shaped 
 like an upright cylinder, and is defined with tolerable 
 sharpness. A disc, therefore, of greater diameter than 
 the circle which would be given by a horizontal section 
 
children's toys. 
 
 113 
 
 of this stream would be proportionately ineffective, since 
 it would have an exterior marginal band of more or less 
 breadth which would constitute a merely passive weight 
 to be | carried round at the expense of the energy of 
 motion of the parts within the range of the current of 
 the hot fountain. 
 
 Windvanes, (or whatever their proper name may 
 be, when they are doing duty on shipboard,) are to be 
 found afloat, for they are sometimes employed to work 
 the pumps of leaky ships, which they do, with the in- 
 tervention of cranks, very serviceably. In a case like 
 this any machine in the shape of a windmill would 
 necessarily be altogether inadmissible, since its long 
 arms would be in perpetual conflict with the rigging 
 and the crew. The wheel ventilators, also, which are 
 fixed in window panes are, obviously enough, in princi- 
 ple, and almost in form, merely windmills or smokejacks 
 doing duty in another sphere. Their object corresponds 
 with that of the discs applied to lamps of which we 
 spoke just now, and is that of modifying the impetuos- 
 ity of the stream of cold air which enters a room, and 
 breaking and scattering its current, so that it may not 
 by a too direct inrush assume the tormenting and 
 deadly character of a draught. 
 
 In London, at the very core of the heart of the City, 
 a windvane is one of the most conspicuous objects, 
 perched aloft over the Eastern end of the roof of the 
 Exchange. By the intervention of suitable mechanism 
 it notifies on a dial in Lloyd's Rooms just below, which 
 are the headquarters of those whose business is con- 
 nected with marine insurances, every variation in the 
 wind as it occurs, the state and prospects of the weather 
 
 i 
 
114 
 
 children's toys. 
 
 being, of course, a matter which, closely concerns the 
 interests both of shipowners and underwriters. 
 
 I have dwelt rather persistently on the nature of 
 the motive power in windmills and other mechanical 
 contrivances of the same order, because as soon as this 
 has been once thoroughly grasped the understanding 
 of a host of toys becomes at once a bit of property in 
 actual possession. That this is so may be shown by 
 examples. 
 
 If you go from here to London by train on a day 
 so perfectly calm that there is not even a breath of air 
 stirring, and if, when you are travelling at fall speed, 
 you put your head out of window, is the air still motion- 
 less ? In one sense it is, because the circumstance of 
 your going to London, whatever interest the fact may 
 possess for yourself, does not affect the weather. The 
 air, therefore, continues to be just as tranquil, as far 
 as the world at large is concerned, as it was when you 
 started, but with regard to yourself and the train an 
 actual hurricane is blowing against you and it. You 
 thus find by experience what, indeed, would have been 
 clear enough without proof, that the result is the same, 
 as far as the action of air upon anything is concerned, 
 whether the object in question stands motionless in a 
 high wind, or itself passes rapidly through a still atmo- 
 sphere. So that if you could put a windmill on the top 
 of the railway carriage, and front it towards the engine, 
 as soon as the train got under way, the sails would be 
 set in motion also. And the faster the speed of the train 
 became, the stronger would be the draught of passing 
 air, and the greater the rapidity with which the sails 
 would turn. A boy who runs with his kite when there 
 
children's toys. 
 
 115 
 
 is not enough wind to raise it, acts, of course, upon the 
 principle of creating by this expedient an artificial 
 blast. 
 
 Here you come upon the reason why a shuttlecock 
 spins as it flies. Its feathers are placed obliquely, so 
 that the wind exerts the same sort of action on them 
 as it does on the sails of a windmill, and turns the 
 shuttlecock round. You saw why a windmill placed 
 with the surfaces of its sails flat to the wind would not 
 act. Nor, of course, would a shuttlecock spin, if its 
 sails, that is to say its feathers, were not arranged so 
 as to stand aslant to the virtual current of air which 
 flows against them. If they are so twisted as to be 
 no longer oblique, the shuttlecock drops lifelessly, with 
 no motion beyond that of mere falling. 
 
 The same is the case with an arrow. The feathers 
 of an arrow are not placed in a line with its length, or 
 parallel to it, but diagonally across the shaft. Hence 
 the result of the factitious blast upon them which their 
 rapid flight through the air creates is to make the arrow 
 spin round an axis which is the central line of its length. 
 Noone, probably, can have imagined that the feathers 
 of an arrow help it to fly, in the sense of aiding its 
 impetus. On the contrary, they necessarily undermine 
 its energy of progression, and act as a drag upon its 
 speed, but this disadvantage is more than counter- 
 balanced by the greater regularity of flight which is 
 induced by the revolution round the axis, so that the 
 shaft can be impelled more true to its mark. Similarly, 
 the shuttlecock, though its alertness in rising and 
 falling is in some degree subdued, which happens to 
 be all the better, by the moderating influence of its 
 
116 
 
 children's toys. 
 
 feathers, is far more steady in its proceedings than it 
 would be if it did not spin. Depend upon it that 
 William Tell would never have been so rash as to 
 attempt to shoot an apple from his son's head with an 
 arrow having no other motion than that imparted to it 
 by the bowstring. 
 
 There is more than one reason why an arrow, or 
 other projectile, travels in a better ordered course for 
 having a movement of revolution at the same time 
 with that of transmission. We shall find a more con- 
 venient opportunity later on of discussing one of the 
 two main causes of the effect in question; the other 
 may be taken in hand and disposed of at once. It is 
 this. No arrow can be made so completely symme- 
 trical, so accurately balanced, so perfectly smooth in 
 surface, and with its feathers so evenly adjusted, but 
 that it carries in its person some little irregularity or 
 other, which, if permitted to work upon it, as a dis- 
 turbing agency, throughout the whole course of its 
 flight, would eventually succeed in compelling it to 
 deviate more or less to one side or the other from the 
 straight line leading towards its proper goal. Even 
 in the case of an ideal arrow faultlessly made, and that, 
 too, of materials of such uniform substance that it 
 would balance with mathematical accuracy about its 
 axis, still it might very probably receive during the 
 short instant which would elapse after it left the string, 
 and before it got clear of the bow and the shooter's 
 hands, a touch or push from some slight prominence 
 or inequality on one of the surfaces over which it would 
 have to pass, which would impair the precision of its 
 aim, It would be impossible to preclude altogether 
 
children's toys. 
 
 117 
 
 the intervention of disturbing agencies of this kind, 
 inasmuch as they are often too small to be dealt with 
 or detected, and they are communicable from a variety 
 of sources external to the arrow itself. 
 
 Now any want of balance or other circumstance 
 which is adverse to the accomplishment of a steady 
 and smooth trajectory, as it is called, that is to say the 
 path which is followed by a missile between its point 
 of departure and the conclusion of its errand, is, as far 
 as possible, rendered of none effect by the spinning. 
 For thereby the element of irregularity, whatever it 
 may be, is brought to exert its power in opposite 
 directions, alternately, in rapid succession, so that it 
 annihilates of itself its own effect. It is for the reasons 
 which have been explained that in the game of cup 
 and ball the player makes the ball spin preparatory to 
 attempting his stroke. To land the ball fairly on 
 the spike demands great exactitude of manipulation, and 
 this is much promoted by the steadiness which the 
 spinning imparts. 
 
 Bullets and cannon balls are rifled on the same 
 principle. In the case of missiles of this description, 
 feathers, of course, could not be employed for imparting 
 the desired rotation. The object is attained, as you 
 probably know, either by cutting the inner surface of 
 the barrel into ridges, not running in straight lines in 
 the direction of its length, but winding round it, or 
 else by scooping two or more parallel grooves, similarly 
 curved, for the reception of a belt or studs projecting 
 from the surface of the ball. The missile is constrained 
 to follow the course which the ridges or grooves impose 
 upon it, and thus emerges from the muzzle imbued 
 
118 
 
 children's toys. 
 
 witli the rotatory motion which it has acquired within 
 the barrel. 
 
 The result which is brought about by a lateral pull 
 of weight, that is to say, by any excess of the heaviness 
 of one side of the projectile over that of the other, when 
 it is not made to counteract i.ts own influence by spin- 
 ning, becomes conspicuously manifest in the game of 
 bowls. Each bowl, for the purposes of the game, is 
 designedly so shaped as to have one of its sides to a cer- 
 tain extent bulkier than the other. When first dis- 
 patched from the hand of the player, and when its for- 
 ward motion is therefore young and vigorous, the bowl 
 is pretty nearly altogether the creature of its dominat- 
 ing impulse, and travels a course which deviates perhaps 
 but little from the rectilinear track along which it was 
 started. This line of projection must necessarily have 
 been a perfectly straight one, as will more fully appear 
 presently when we come to discuss another subject which 
 lies but a short distance before us. The initial liveli- 
 ness of movement, however, soon begins to sober down, 
 as it gets tamed and worn by friction, and by other agen- 
 cies which undermine its vitality ; and the bias, as it is 
 called, that is to say the influence of the overplus of 
 weight which the bowl carries, so to speak, in one of its 
 two side pockets, comes into play with an effect which 
 was at first imperceptible but now becomes manifest. 
 The lateral deflection grows more and more marked as 
 the energy of progress declines ; the path which is tra- 
 velled rapidly shrinks from a broad sweep into a narrow- 
 ing, and eventually sharp curve, till at last the bowl 
 comes to a standstill very much after the familiar fashion 
 in which a dog gets to rest by wheeling round and round 
 
children's toys. 
 
 119 
 
 in a sort of spiral coil, till he makes a final turn so con- 
 tracted as to be almost within the length of his own tail. 
 A plate or basin trundled along the floor behaves in a 
 like manner and for similar reasons. 
 
 We will now turn to two toys which act, speaking 
 generally, on precisely the same mechanical terms as 
 windmills, and smokejacks, and the rest of the family 
 of contrivances of which we have just spoken, in which, 
 as has been seen, a revolving motion is produced by 
 air acting on sails, or sheets of metal, disposed obliquely 
 to its course. The principle involved has been already 
 dwelt upon so much that we may pass over very rapidly 
 instances of its employment similar to those which 
 have been already considered. 
 
 One of the toys in question which we have not yet 
 dealt with is a flying top, as it seems to be called at the 
 shops where such things are sold. It is, as you see, an 
 affair which looks like a four-winged butterfly, or a cross 
 between some insect of that kind, and a windmill, and 
 it is furnished with a shank and other arrangements 
 which need not be more particularly described, so that 
 it can be wound up like a common top. When this is 
 done and the string is pulled, the top is, as will be found, 
 fired with an impulse to start somewhither. It strives to 
 
120 
 
 children's toys. 
 
 leave the handle, or to burrow down into it, according 
 as it is made to spin in one direction or the other. The 
 first question which its conduct suggests is that of 
 why it does not spin contentedly where it is, without 
 either trying to rise to the ceiling, or evincing a solici- 
 tude to get down to the floor. To understand this, 
 attention must first be directed to what is perhaps the 
 very simplest and most elementary fact in mechanics* 
 and which is expressed by the statement that " Action 
 and Reaction are equal and opposite."" 
 
 Before examining the proposition which has been 
 just enunciated, let me give you a word of caution 
 against being misled into erroneous conceptions of the 
 terms Action and Reaction. The employment of these 
 words, which treacherously cover fallacious suggestions 
 as to the true nature of the occurrences which they pro- 
 fess to describe, is a misfortune, but we cannot alter or 
 dispense with them. If you consider for a moment the 
 notions which the words are calculated to convey, and 
 what the real truth of the matter is in the position of 
 affairs as to which they are used, you will be proof 
 against any misleading tendencies which they might 
 otherwise exert. 
 
 That Action and Reaction are equal and opposite 
 means that whenever any object or body strikes, 
 presses, or pulls another, the force which is exerted 
 by either of the parties to the encounter is met at any 
 and every point where they are in collision or contact 
 by a direct and corresponding resistance. 
 
 I hold in my hand a book. It weighs, say, a pound. 
 I put in action in supporting it a force which may be 
 defined as one of alb., since the measure of its strength 
 
children's toys. 
 
 121 
 
 is accurately thus indexed, and the weight of the book 
 exerts a reaction, pressing downwards on my hand 
 with a like degree of energy. A horse drawing a cart, 
 to borrow an illustration given by Sir Isaac Newton, 
 is pulled back by the traces to the precise extent of 
 the power which he employs. A schoolmaster gives a 
 boy a box on the ear. The boy's ear returns, and at 
 once, the compliment to the schoolmaster's hand with- 
 out either interest on, or discount from, the degree of 
 violence, whatever it may have been, to which it has 
 been itself subjected. If it were to be urged that this 
 cannot be so because the ear receives a painful blow, 
 while the hand does not suffer in any corresponding 
 manner, such an argument would be based on confused 
 notions of the occurrence. The ear and the hand strike 
 one another with precisely equal force, but the sensa- 
 tions which are excited by the collision are more 
 acutely felt by the former because it is the more tender 
 of the two. If I push against a wall, the wall gives me, 
 in return, a shove which is just as decided as my 
 own. 
 
 If you were to controvert the assertion that when 
 a body which is in motion strikes another which 
 is at rest, the aggressor gets as hard a knock as the 
 victim of its onslaught, you would find yourselves 
 committed to all sorts of absurdities. You would 
 have, for example, to admit that a bullet which is fired 
 at an iron target, and hits it, commits self-destruction 
 when it is beaten flat by the stroke. The bullet is 
 knocked so completely out of shape that its most inti- 
 mate friends would now fail to recognise it. Did it 
 batter itself into the likeness of a sixpence by some 
 
122 
 
 children's toys. 
 
 suicidal act, or else how was its present abject con- 
 dition induced ? The iron plate against which it was 
 shot positively and actually struck in its turn, and the 
 result was such as would naturally ensue from a blow 
 from such a source, when virtually wielded as a hammer 
 with a force equal to the impact of the bullet. 
 
 It is expedient to detain the matter which is now 
 under our hands sufficiently long to possess ourselves 
 with a full, clear, and firm apprehension of it, because 
 Reaction, generally speaking, does not get its fair share 
 of recognition. Its ojoeration is apt to be entirely 
 overlooked by those who have not been in the habit of 
 considering mechanical problems, in all of which, of 
 course, it plays a part of prime importance. In a great 
 many cases we set Action going solely for the purpose 
 of creating Reaction, because it is this latter which we 
 wish to call up to do some particular service for us within 
 its own department. 
 
 A case in point is that of a rocket. What is it which 
 causes a rocket to leap into the air ? To a great extent 
 Reaction. The carcase of a rocket is made of stout cart- 
 ridge paper rolled into the shape of a hollow tube. The 
 material is light, and at the same time its inner surface 
 will stand contact with a good deal of hot name for a few 
 moments without being itself consumed. The tube is 
 filled with a mixture of combustible powders of kinds 
 such as will burn vehemently, and produce a torrent of 
 sparks, which are wanted, to form the tail. This com- 
 pound, when set alight, produces a sudden and intense 
 heating, and consequent expansion of the air in the tube 
 exactly as gunpowder does, in a still more vehement and 
 instantaneous manner, in the chamber of a gun. The 
 
children's toys. 
 
 123 
 
 dilated air, together with the elastic gas which has been 
 generated by the combustion, not only presses upwards, 
 but rushing in an impetuous stream out of the open 
 end of the tube, thrusts downwards against the atmo- 
 sphere outside, and carries the rocket in whatever 
 direction its head may be pointed. 
 
 In a gun the whole force which the explosion of its 
 charge of powder is capable of generating is called into 
 being, accomplishes its entire life's work, and dies, 
 within the space of one short instant. This force acts, 
 of course, upon the interior of the gun itself, as well as 
 upon the hind-quarters of the shot, and causes the recoil. 
 In the case of a rocket, no sudden spasm of force is 
 aroused, so that there can be no bursting of a barrel, and 
 the inconvenience of a recoil is avoided, since 'the air, 
 as will be seen, taking the place of the breech, there is 
 nothing to be driven backwards, but the projectile 
 makes its own way by a comparatively gentle, but 
 sustained, push from the rear. It may be mentioned 
 that in Hale's military rockets the backward rush of the 
 gases engendered by the combustion in the tail is so 
 directed as to impart a spinning motion to the projectile, 
 thus giving it the precision of flight which belongs to 
 rifles. The rocket propels itself just as a man punts a 
 boat along a river. The boat represents the firework ; 
 the shove given by the puntsman answers to the impulse 
 generated by the stream of hot air arising from the 
 blazing of the combustibles in the rocket's tail, and the 
 bottom of the pond, which returns poke for poke through 
 the oar or pole which is used as the instrument of pro- 
 pulsion, behaves, mechanically speaking, precisely after 
 the fashion of the reacting air. 
 
124 
 
 children's toys. 
 
 The revolution of a Catherine wheel is imparted to 
 it by a similar agency, which, by the way, is as old as 
 the Creation. To adduce but one instance out of in- 
 numerable illustrations of the fact just stated with 
 which natural history teems, it may be mentioned that 
 the Nautilus is not, as generally supposed, a sailing boat, 
 but a rocket, for its real method of progression is far less 
 picturesque but more practical than that with which it is 
 credited. It does not spread a delicate membrane like 
 the sail of a fairy ship to the breeze, but sucks in and 
 afterwards squirts out backwards a stream of water from 
 a narrow tube which forms a part of its personal ar- 
 rangements, and thus, in short, punts itself along. 
 Steamboats propelled after the fashion which is exem- 
 plified in the nautilus are to be seen upon the Thames. 
 The original source of motion is, of course, the steam 
 engine, which corresponds in this particular with the 
 muscles of the animal, but the immediate instrument 
 whereby progression is actually achieved is a stream 
 of water, which is sucked, or allowed to flow, into a 
 suitable receptacle, and thence discharged through a 
 pipe in a vehement stream in the direction, whatever 
 it may be, opposite to that towards which the boat is 
 intended to go. 
 
 Watermills have been constructed on 
 the same principle. The most familiar 
 machine of this particular kind is known 
 as Barker's Mill. The water is admitted 
 from above into a hollow cylinder, poised 
 vertically on a pivot, and escapes thence 
 through holes bored in the sides of 
 tubes projecting horizontally from the base. The jets 
 
children's toys. 125 
 
 which, are thus formed generate, for reasons already 
 indicated, forces directly contrary to their own courses. 
 Their combined effect upon the tubes which are, in 
 effect, handles of a windlass, and arms of a lever, is 
 sufficient to make the cylinder spin. The whole con- 
 trivance is an expedient for obtaining from a perpen- 
 dicular fall of water a circular and horizontal motion, 
 such as is capable of direct appliance to the task of 
 grinding. The earliest form of steam engine, com- 
 monly known as Hero's, was a machine in which the 
 mainspring of power was obtained through the same 
 principle as that on which the action of a Catherine 
 wheel, or a Barker's Mill, is founded. Turbines, which 
 are also hydraulic engines, give a sufficiently clear in- 
 dication of the nature of their source of action by their 
 sub-title of " reaction wheels." 
 
 It should be mentioned that in all the contrivances 
 of which we have been speaking during the last few 
 minutes, the whole of the motion with which they are 
 animated when set going is not exclusively referable 
 to the source to which alone for the sake of convenience 
 and simplicity it has been assigned. Their action 
 might, indeed, be regarded in a different view, as 
 follows. The principle of their contrivance is, it might 
 be said, the generation of pressure, and its subsequent 
 relief in one quarter only, that, namely, which is 
 opposite to the direction towards which motion is 
 sought to be produced. The result necessarily ensues 
 of movement due to giving, or yielding, in compliance 
 with the promptings of the unweakened forces which 
 now come to prevail. The explanation, however, 
 which was first propounded is not incorrect as far as it 
 
126 
 
 children's toys. 
 
 goes, and it was adopted as being illustrative of reaction 
 as a moving force. 
 
 To return now to our flying top. When you make it 
 spin very rapidly, its wings strike the air, which returns 
 their blows with a spirit and effect precisely equal to 
 their own. The pinions are set, and the blows given, 
 slanting, so that the reaction is oblique also. If you 
 seek to know what the effect hence produced on them 
 must be, this can be ascertained in a moment by pick- 
 ing to pieces the forces concerned in the transaction 
 by means of a parallelogram drawn after the recipe 
 which was given just now, for solving problems of this 
 description. It will then be found that the result in 
 question must be to carry the top in one direction or 
 another, according to the manner and attitude in which 
 it has been spun. Conceive that the top had but two 
 wings instead of four. Would it still fly ? Judging by 
 analogy it would, because although most insects have 
 four wings, birds have but two. We may assume, 
 therefore, that if we have a two-winged top and point 
 its nose horizontally, that is to say so as to direct its 
 course along a track lying level between the ceiling 
 and the floor, it will fly accordingly. Now imagine it 
 to be linked with the handle from which it is set 
 going, so as to be all of a piece with it. The latter 
 will then be pulled along or pushed backwards, accord- 
 ing to the manner in which the top is spun. The toy 
 is now seen to be in fact an exact model in miniature, 
 as far as its principle of action is concerned, of a screw 
 steamer. It is, mechanically speaking, the same thing. 
 
 There is just one point on which it may be as well 
 to bestow some notice here. In a ship's screw there 
 
children's toys. 
 
 127 
 
 are usually only two " limbs/' as they are called, and 
 it is not of itself apparent why windmills should have 
 never less than four sails, while screws have mostly, 
 like some of the rough specimens of these toys, but 
 two. In the case of the toys the explanation is that 
 myriads of them are made to sell wholesale at a good 
 profit for a penny each, and nobody could 
 expect to be able to buy at so low a price 
 the most perfect thing of its kind which 
 could be turned out, but merely the sim- 
 plest article which will work. In the case 
 of ships' screws the advantage which is 
 generally found in limiting them to two 
 limbs is readily to be accounted for. We 
 cannot diverge into an examination of that 
 matter here, as it does not fall quite within the range 
 of our proper business this evening, and I merely 
 advert to the point of the small number of the limbs 
 in the ordinary marine screw to show that it has not 
 been overlooked. 
 
 There is one other subject which ought perhaps to 
 be noticed under the head of screws. A question may 
 occur to some of you as to how it is that screws are 
 used . at all for moving ships. It might be thought 
 that since they act obliquely, power must therefore be 
 wasted, the reaction on them which constitutes the 
 forward impulse not being in a line with the course of 
 progress of the vessel. The employment of paddle 
 wheels might thus seem to be more economical of force, 
 because these latter may appear to push straight back- 
 wards against the water. The answer is that a paddle 
 wheel is as prodigal as a screw in its waste of 
 
128 
 
 children's toys. 
 
 mechanical energy. Examine, for instance, the case of 
 any one of the flat boards, or " floats/' as they are 
 commonly called, which are ranged within the outside 
 rim of such a wheel. If you investigate its precise 
 course of conduct you will perceive how much fruitless 
 labour it squanders. Now whatever any individual 
 float does in this respect, all its fellows on the same 
 paddle wheel must do too, since they are all just alike, 
 are all similarly placed, and all behave in the same 
 manner, so that anything which may be found to be 
 true for one will necessarily apply to all. Thus if the 
 futile expenditure of power which is to be laid to the 
 account of any one of them be multiplied by the 
 number of the whole set, the sum of the waste on the 
 part of the entire paddle wheel will have been ascer- 
 tained. To come now to particulars. 
 
 When the float first comes into contact with the 
 water, it strikes it pretty nearly flat, and presses it 
 almost straight downwards. The resistance which it 
 evokes on the part of the water is a reaction which is a 
 force in the opposite direction, that is to say almost 
 entirely upwards. This latter does next to nothing 
 towards propelling the vessel forwards, but simply and 
 vainly tends to lift it. As the float gets buried deeper 
 and deeper by the revolution of the wheel, its action 
 assumes more and more a horizontal direction, such as 
 is needed for pushing the water backwards, and the re- 
 action upon it goes through corresponding changes 
 towards a force of direct propulsion. When the float 
 arrives at its lowest position, that is to say when it is 
 vertical, it then at last acquires for the first time a capa- 
 city for exerting action which is altogether calculated to 
 
children's toys. 129 
 
 serve its intended purposes. But at this juncture it is 
 already half through its whole period of immersion, 
 during which alone it can do any work at all. Nor 
 does it retain the advantage of the position in question 
 for a single entire moment, for with even the smallest 
 possible degree of further revolution of the wheel, the 
 outside edge of the float is instantly brought a little 
 upwards, and purely horizontal action is thereupon 
 lost at once. Much of the float's force is thencefor- 
 wards vainly spent in lifting a quantity of water, which, 
 by its reaction and weight, tends only to depress the 
 ship. 
 
 The action of a paddle wheel is thus attended by a 
 serious waste of power lavished idly in scooping, as it 
 were, a great hole in the sea, but this is not the only 
 disadvantage which is incident to it. A second main 
 objection to which it is open is one with which our 
 present inquiries have no concern, but it will be more 
 satisfactory to make a short divergence to it so as to 
 wipe up the subject of paddle wheels with a nearer 
 approach to completeness. 
 
 The violent downward battering on the water in 
 front, and the laborious upheaval behind, cause the 
 machinery to strain and vibrate in an uncomfortable 
 and injurious manner. An attempt is sometimes made 
 in the case of large ships to mitigate these inconveni- 
 ences by what are called feathering paddle wheels in 
 which the floats shift their attitude in such a manner as 
 that they keep always vertical ; but the friction of the 
 machinery which is required for procuring this con- 
 tinued fresh adjustment is so great as to make extrava- 
 gant demands on the engine -power on its own separate 
 
 K 
 
130 
 
 children's toys. 
 
 account. Another device, therefore, is frequently- 
 adopted which aims at relieving, though it does not 
 attempt to exclude, the mischief complained of, and 
 which consists in using what may be called composite 
 paddle wheels. Bach of such wheels is made up of two 
 or three narrow ones joined together at their sides. The 
 floats of these several wheels are so arranged as not to 
 be in straight lines with their neighbours. It will be 
 perceived at once that the effect of this contrivance is to 
 render the action upon the water of the composite wheel, 
 as a whole, less intermittent, and thus more equable and 
 gentle than is the case with the simpler form of construc- 
 tion. The blows and lifts on the part of the floats are, no 
 doubt, in their aggregate mechanical effect, alike for 
 both cases, the total area of surface which encounters the 
 water being the same ; the shocks and strains, however, 
 are mitigated by subdivision, that is, through being 
 broken up, so that they become components of a 
 closer-packed series of collisions, which are more 
 numerous indeed, but individually of less violence. 
 
 The end which is sought by the employment of com- 
 posite paddle wheels is occasionally pursued by other 
 contrivances, such, for example, as that of breaking up 
 the broad surface of the float into stages by substituting 
 for the single board, of which in its plainest form it 
 consists, several comparatively narrow strips of wood, 
 arranged after the manner of steps in a staircase. The 
 abruptness of encounter with the water is thus miti- 
 gated, as the whole shock of impact is reduced into the 
 form of a series of what may be termed little slaps, 
 instead of heavy bangs, and the total effect of these is 
 distributed over a certain space of time. But all these 
 
children's toys. 
 
 131 
 
 matters are far off our proper track, to which we should 
 at once return. 
 
 A paddle wheel is identical in form with the wheel 
 of an undershot watermill. Moreover, if you consider 
 the action of the stream upon such awheel when doing 
 duty in connexion with a mill, you will notice that it is 
 subject to just the same disadvantages in respect of 
 waste of power as is the case when it is officiating as 
 the propeller of a ship. It appears, therefore, that as 
 a windmill, mechanically speaking, is the counterpart of 
 a steamer which is driven by a screw, an undershot 
 watermill corresponds in the same manner with a ship 
 which is impelled by paddles. The flight of stairs 
 wrapped round a cylinder which is the main feature of 
 a treadmill, is identical, mechanically speaking, with an 
 overshot waterwheel. 
 
 Our disquisition on screws and paddles would form 
 a natural introduction to an inquiry into the conditions 
 of the propulsion of boats by means of sails and oars. 
 And it would be quite proper to glance at this topic as a 
 branch of our task of this evening because boats are 
 among the most common and popular toys. But since 
 the main use of a lecture, as the author of " The cor- 
 relation of the physical forces " says, (my recollection 
 of his precise words is imperfect, but I am not sure that 
 he does not put the proposition so broadly as to say the 
 " only " use of a lecture,) is to incite and to help people 
 to investigate for themselves, the subject of oars and 
 sails, being rather a large one, had better be remitted to 
 the category of those which we will put aside to be looked 
 into by any of you who may have been led to feel some 
 interest in the matters with which we have been busy. 
 
132 
 
 children's toys. 
 
 If what has been said about windmills and other cog- 
 nate machines has not been altogether in vain, what- 
 ever secrets maybe latent in the operation of sails and 
 oars will be quite easily caused to reveal themselves. 
 
 A good deal of discussion has taken place of late 
 years on the subject of vivisection, that is to say on the 
 question whether it is right to allow experiments to be 
 made on the bodies of living animals for the advance- 
 ment of the knowledge of physiology ; to inflict, in 
 short, a certain limited degree of pain or injury on 
 certain creatures for the purpose of gaining such know- 
 ledge as will, among other advantages, enable us to 
 reduce the aggregate of suffering which would other- 
 wise be the lot, not of humanity only, but of the whole 
 community of sentient beings. Whatever opinion may 
 be held on the points in dispute, nobody, at any rate, can 
 possibly object to our vivisecting a live force, and thus 
 discovering of what it is, or may be, made of, and how 
 the various sinews which go to form its composition 
 are likely to affect objects with which they are put in 
 relation. Since you must now be taken to be expert 
 practitioners in mechanical surgery of this innocent 
 kind, you may profitably subject a wind of any specified 
 power to dissection, and ascertain the force which it 
 is calculated to exert, when blowing from any given 
 quarter, upon a sail of any stated dimensions, and 
 stretched in any defined position and attitude. You 
 may further determine how the sail, thus wrought upon, 
 will tend to produce motion, and of what kind and 
 amount in any particular ship to which it is attached. 
 
 Before taking leave of boats it may be pointed out 
 that an angler who uses artificial bait will perceive an 
 
children's toys. 
 
 133 
 
 illustration of the action of a ship's screw in the spin- 
 ning fish with which he captures pike and trout. The 
 means by which the peculiar movement which is requi- 
 site is imparted to the bait has been sufficiently indi- 
 cated. For it has been shown that if a windmill were 
 to be carried on a train going at speed the sails would 
 be put in revolution by encountering a virtual gale of 
 wind. And for similar reasons it is plain that a marine 
 screw, if it were to be wholly abandoned to the action 
 of the water upon it, would revolve, if the ship to 
 which it belonged were moored in a flowing stream, or 
 were to sail, or be towed, over a still lake. In fact, 
 the commonest method of ascertaining the speed of a 
 vessel is by noting the number of revolutions made 
 within a given time by an instrument of the character 
 of a screw, dragged astern, and turning freely in com- 
 pliance with the action of the water which in effect, 
 under such circumstances, streams against it. 
 
 This last mentioned contrivance is identical in the 
 nature of its springs of conduct with an artificial min- 
 now. The counterfeit fish is fitted with metal append- 
 ages having the semblances of a tail and of fins standing 
 out obliquely to its length, so that when drawn against 
 the water it spins rapidly. This, of course, is just what a 
 real fish does not do, for such a movement could not fail 
 to make him extremely giddy , and addle what little modi- 
 cum of brains he may possess. But through the blurring 
 effect of " persistence of vision " in the eye of a jack 
 or trout, the true nature of the bait's movement is in- 
 discernible, as is also, for the same reason, the deceptive 
 personality of the minnow itself, which often, indeed, 
 is not even made, otherwise than in its general sort of 
 
134 
 
 children's toys. 
 
 outline, in the likeness of a fish at all. Similarly, the 
 hooks with which the bait is profusely armed, if they 
 are visible at all, are but dimly so, presenting only the 
 appearance of an indistinct steel-coloured halo en- 
 veloping the body of the object to which they are at- 
 tached, so that their real character is effectually masked. 
 The spinning contributes also something towards the 
 successful mimicry of nature by making the gestures 
 of the bait more composed and fishlike than they would 
 otherwise be, since the axis of rotation, as was noticed 
 in the case of an arrow, and as will appear more fully 
 bye and bye, has a tendency to maintain itself unaltered. 
 
 It is under such deluding conditions as these, there- 
 fore, that a hungry pike or trout catches a glimpse of a 
 fleeting object, which is not clearly determinate to 
 sight, but which seems to be of about the size, shape, and 
 brightness of the minnows or gudgeons which are his 
 usual prey, and which swims to all appearance after the 
 orthodox fashion of such creatures. Ignorant, there- 
 fore, of the wiles of anglers, he makes his snap at the 
 bait, and gets caught. It would hardly perhaps afford 
 much consolation to the poor wretch, as he lies gasping 
 upon the bank, to be told that he has unwittingly had 
 the honour of illustrating in his own person, as by a 
 working diagram, the practical effect of some of the 
 scientific principles which we have lately been con- 
 sidering. 
 
CHAPTER V. 
 
 N thinking over the list of toys to be spoken 
 of this evening, I should hardly, if the selec- 
 tion had rested with my own uninstructed 
 judgment, have included pumps among 
 them, and still less fire engines. Such things as these 
 would have been taken to belong essentially to the 
 domain of serious life and business, and to be con- 
 cerned with the sober interests and necessities of grown 
 up people only. But on looking in at the windows of a 
 great number of toyshops for the purpose of learning 
 what were really the principal features of their contents, 
 I found, rather to my surprise, that not only squirts, but 
 small working hydraulic machines of the kinds which 
 have been mentioned, were everywhere to be found in 
 great abundance, so that they preferred a claim, which 
 could not fairly be disallowed, to take rank among the 
 very commonest and most favourite playthings of all. 
 Such being the case, it was clear that any disquisition 
 on toys from which these particular ones were to be 
 omitted would be as wanting in completeness as a novel 
 without a heroine. 
 
 The reason of the warm popularity of toys which 
 
136 
 
 childken's toys. 
 
 have to do with, water is readily to be descried in the 
 keen delight which children find in making a mess. So 
 universal is this juvenile passion that there is no im- 
 propriety in conceiving that even the most august per- 
 sonages, such as the Queen when she was a little girl, 
 and the Archbishop of Canterbury when he was a little 
 boy, must have revelled in making mud pies, or at any 
 rate must have longed to enjoy that pastime, if the 
 natural tendencies of children were healthily developed 
 in them. A squirt has hence a claim to full examination 
 as an especially popular favourite ; moreover a real, and 
 not merely fancied, understanding of it is the necessary 
 half-way house on the road towards a knowledge of 
 other toys and contrivances which are based on similar 
 principles, but whose construction is not quite so simple. 
 
 There is a creature called a marine ascidian, better 
 known by its popular name of a sea-squirt, though its 
 conformation is more nearly akin to that of a pair of 
 bellows, which belongs in about equal degrees to both 
 the animal and vegetable persuasions. According to 
 Mr. Darwin, marine ascidians possess the same kind of 
 direct ancestral relationship to humanity as squirts do 
 to fire engines. We are all of us pronounced to be 
 ascidians, only that we are gifted with a more elaborate 
 complexity of bodily structure than belonged to our re- 
 mote forefathers ; a condition which we have gradually 
 acquired in the course of a long series of ages and 
 descents. It behoves us therefore to view all branches 
 of the great family which bears the name of Squirt with 
 proper respect. 
 
 A squirt, as everybody knows, is charged by im- 
 mersing its spout in water, and then drawing out its 
 
children's toys. 
 
 137 
 
 handle. As this is done, the water enters, nor will it 
 run out again, whatever may be the position in which 
 the instrument be held, until it is forcibly ejected by 
 pressure brought to bear upon it through the handle. 
 The first point which arises for consideration when 
 these facts have been noticed is that the water first 
 runs upwards, and then refuses to flow down through an 
 open pipe though not restrained from so doing by any 
 visible obstacle. Behaviour like this is out of con- 
 formity with the usual conduct of all liquids, which, 
 being amenable to the attraction of gravity, never 
 mount a hill of their own accord, and always course 
 down an incline when the road is open. The pheno- 
 menon is to be accounted for in a very simple 
 manner. 
 
 The body of the squirt is a tube of smooth 
 and uniform bore, and it is furnished with what 
 is called a piston, that is to say a plug, fitting 
 its interior so closely as not to allow air to pass 
 between its outside edge and the surface with 
 which it is in contact, but yet not so tightly 
 jammed as to prevent it from sliding comfort- 
 ably up and down. The piston is moved by a 
 rod, working through a tolerably loose collar at 
 the closed end of the tube. This covering of 
 one end of the tube is no essential part of the 
 constitution of a squirt. The object of the ~ 
 arrangement is merely one of convenience, and 
 it is twofold ; first, that of preventing the piston from 
 being dragged right out of the tube by too long a 
 stroke, and secondly, that of keeping the rod, while in 
 action, in its proper posture, which should always, of 
 
138 
 
 childeen's toys. 
 
 course, be parallel to the surface within which it works, 
 taken lengthwise. 
 
 When the piston is pulled back, it drags before it 
 all the air which was inside the tube, and conducts 
 it out through the collar. Thereupon if the passage 
 through the nose of the squirt be free, other air enters 
 by it, and supplies the place of that which has been 
 withdrawn. The entering air follows close on the heels 
 of that which retires. Why it thus conies in seems 
 nowadays to be so obvious that it sounds like trifling to 
 propose to talk about it at all, and yet it is only quite 
 lately, comparatively speaking, that the true nature of 
 the proceeding has been recognised. The so-called 
 explanation formerly given was that the outside air thus 
 enters because, as it was quaintly and mysteriously ex- 
 pressed, " Nature abhors a vacuum." A vacuum, as 
 you know, means a space empty of everything, air in- 
 cluded, and the assumption which was made, and which 
 was quite gratuitous, and unsupported either by proof 
 or likelihood, was that Nature, in a spirit of blind 
 caprice, is animated by some peculiar antipathy of her 
 own, of which no reasonable account can be given, to 
 the existence of a void. 
 
 To render such a theory as this capable of holding 
 any water at all, the shadowy sort of abstraction which 
 we call Nature, meaning by the term the settled order 
 or law of creation, had to be endued in thought with an 
 actual personality and with small mental weaknesses, 
 since vagaries of sentiment, such as that of disliking 
 empty places, could not, without a violent spasm of 
 imaginative fancy, have been conceived to be felt by a 
 mere dry state of facts relating to the Universe. It was 
 
childeen's toys. 
 
 139 
 
 held, however, that whenever any space becomes empty, 
 the substance, whatever it may be, which happens at 
 the moment to be closest to the spot in question, hurries 
 in to fill the void, unless it be restrained from so doing 
 either by its own rigidity of figure, or by some other im- 
 pediment. This sham of an explanation explained no- 
 thing, and was doubly inadmissible. It implied, as will 
 be seen, that inanimate things are nevertheless amenable 
 to a sort of moral compulsion, for it alleged that, in 
 deference to a supposed edict of Nature, they, passive 
 though they must always be in the hands of forces which 
 they have no power either to generate or control, still, in 
 one particular case only, take action of themselves under 
 the influence of a special motive. Or, if the doctrine 
 was that the movement in question was to be taken as 
 somehow or other originated by Nature, this theory 
 was wholly bereft of any possible meaning whatsoever. 
 For the term " Nature," when thus used, merely made 
 a vague suggestion of some unknown agent, without 
 pretending to define the machinery by which its ends 
 were brought about. 
 
 The true account of the matter of course is that it 
 is altogether a mere question of simple physical forces 
 whose mode of operation is perfectly clear. It has thus 
 nothing to do with any erratic predilections attributable 
 to an imaginary old lady, called Dame Nature. A right 
 view of the case was accidentally brought about by the 
 following occurrence. A pump had been erected in the 
 palace of a certain Grand Duke of Florence, and al- 
 though the job had been done by the Court plumber, 
 and the apparatus was unexceptionably good of its 
 kind, the water obstinately, and, as was thought* 
 
140 
 
 CHILDBEDS TOYS. 
 
 unconscionably, declined to rise to the spout, which was 
 rather more than 32 feet above the cistern. Galileo, 
 who was living close by, was applied to to explain the 
 enigma of the failure. He was then a very old man ; and 
 although he seems to have scented the real secret of the 
 difficulty, he had probably become too much past work 
 to put his surmises to the test of experiment. He there- 
 fore contented himself with merely throwing out a hint 
 on the subject, as a clue to be followed up by his pupil 
 Torricelli. The latter in due time elucidated the whole 
 thing clearly enough, and showed the weight of the 
 atmosphere to be the real beginning, middle, and end 
 of the whole mystery. 
 
 It has been already stated that if a vacuum is created 
 inside the squirt by pulling out the piston, air imme- 
 diately enters from the outside through the nose, if that 
 passage be free, to supply the place of that which has 
 been withdrawn. This is a consequence of two facts, 
 the first of which is that air, as Torricelli discovered, 
 has weight, and the second, that fluids press equally in 
 all directions. The latter proposition requires a little 
 expansion in order to make it thoroughly clear and 
 familiar to the mind. 
 
 A fluid may be defined to be a material body, or 
 substance, whose parts are separable, and moveable 
 among one another by any force, however small. Do 
 not confound the meanings of the words "fluid" and 
 "liquid" by treating them as altogether convertible 
 terms. Air and water are both fluids, but the latter is 
 also a liquid, which the former, except in poetical 
 language, which has a licence to be vague, is not. The 
 opposite to a fluid is not a "solid," but a "rigid" 
 
children's toys. 
 
 141 
 
 body, that is to say an object, or substance, whose 
 component parts are incapable of altering their relative 
 positions. A force applied to any point of a rigid body 
 is transmitted in one direction only. A force applied 
 to any point of a volume of fluid is transmitted equally, 
 that is to say with undiminished vigour, to each and 
 every particle of the whole mass, that is to say, in all 
 directions. The foregoing statement is made in very 
 rough and general terms only, and would require limit- 
 ing and qualification before it could properly be taken 
 as the basis of reasoning on all matters relating to the 
 mechanical properties of fluids. It will, however, serve 
 our purposes of this moment, as being true in the broad 
 sense in which only we shall employ it. 
 
 It will be a repetition of the same statement, rather 
 than a deduction from it, to say, further, that fluids press 
 equally in all directions. The atmosphere, therefore, 
 gravitating downwards from the sky by its own weight, 
 presses, as being a fluid it is bound to do, in all directions, 
 including upwards, at the aperture of a squirt's nose, 
 whatever may be the posture in which the instrument 
 is held. It is kept at bay at that point by the equal 
 and contrary pressure of the air already inside the tube, 
 which, on its part, similarly derives its power of resist- 
 ance from the weight of the atmosphere above. For 
 this operates upon the piston on the quarter where the 
 rod joins it, and through it on the fluid beyond with 
 which the underside is in contact. Whenever, by the 
 raising of the piston, the force which supports the re- 
 sistance of the air inside the nose of the squirt is with- 
 drawn and nullified, the balance of contending energies 
 is upset, and the victorious power outside brings in 
 
142 
 
 children's toys. 
 
 some of the external atmosphere, which thus follows 
 close on the heels of that which is in retreat. Con- 
 sider this history of what has been supposed to have 
 occurred as necessarily repeating itself at the con- 
 juncture when the nose of the squirt is immersed in 
 water, and the reason why the tube fills with liquid 
 when the piston is retracted becomes at once ap- 
 parent. 
 
 The squirt is popularly said to " suck." Beware of 
 this expression, which, as tending to convey a mislead- 
 ing notion of what takes place, is a treacherous one. 
 Neither the squirt, when it fills with water, nor a per- 
 son who sucks an orange, acts directly upon the liquid 
 which enters the tube or mouth, as the case may be. 
 In either process the real character of the operation is 
 to relieve an inclosed spot of the surface of the liquid 
 which is to be exhausted from the weight of the atmo- 
 sphere, which therefore acts afterwards, all round, only, 
 and not upon, the place in question. Its pressure, thus 
 applied, does the practical work which is required by 
 impelling the liquid in the direction where alone its 
 passage encounters no resistance, that is to say towards 
 the vacuum which the mouth, or piston, has created. 
 To suck up any fluid, therefore, in the sense of drawing 
 it by the direct action of any machinery, or of any com- 
 bination of mouth and breath, is a process which, al- 
 though it sounds as if it were the very simplest operation 
 which could possibly be performed — so simple, indeed, 
 that even an infant is thought to be necessarily obliged 
 to execute it before it can obtain its very first taste of 
 its mother's milk, is yet a feat which, if the popular 
 understanding and interpretation of the term were to 
 
childken's toys. 
 
 143 
 
 be accepted, has never yet been, and never can be, 
 accomplished. 
 
 The squirt is now full of liquid. Water is heavier 
 than air, and therefore if the piston were absent, the 
 squirt would not keep full when its nose was held down- 
 wards, but the posture of affairs which has to be con- 
 sidered is as follows. The air, as has been said, weighs 
 or leans upon or against every point which it can reach 
 either by the way of direct contact, or by transmitting 
 its pressure through any substance or thing, whether 
 rigid or fluid, which will yield to its impulse, or convey 
 this onwards. It thus pushes through the open nose of 
 the squirt against the under surface of the water inside, 
 but it is precluded from acting on the upper side of the 
 mass of liquid by the interposition of the piston. The 
 piston is not amenable to .downward pressure at the 
 present moment, since it is held up by the hand, or 
 maintained where it is by the agency of another extra- 
 neous power, namely that of friction, of which more 
 anon. There being, therefore, nothing to counteract 
 the sustaining action of the air but the weight of the 
 water, which is here a force of inferior energy, the cylin- 
 drical column of which it consists being but a short one, 
 the necessary consequence is that the liquid, like a good 
 citizen " obedient to the higher powers/' does not avail 
 itself of the exit which the open nose of the squirt 
 appears to offer. 
 
 Precisely the same thing happens in the case of our 
 old friend, or, as, perhaps, it might more properly be 
 called, our ancient enemy, the shower bath. At the top 
 of the institution in question is a reservoir, closed above, 
 but having its cover furnished with a valve, that is to say 
 
144 
 
 children's toys. 
 
 a little door, opening at the pull of a string. The bottom 
 of the cistern is pierced with a multitude of little holes, 
 as in the rose of a watering pot, to which the shower 
 bath bears a close relationship both in its personal 
 appearance and its ways. Until the valve is opened the 
 water is sustained in the cistern by the pressure of the 
 outside air, which as yet can act upwards only. When 
 the patient inside the curtains summons courage to pull 
 the string, and thus open the valve, he thereby admits 
 air to the upper surface of the water in the cistern. The 
 upward and downward pressure of air below and above 
 now counterbalance and mutually destroy one another's 
 effect, and the water being thus practically freed from 
 the controlling action of any atmospheric force, becomes 
 obedient solely to gravity, and descends by its own 
 weight. 
 
 To give one more illustration of the same matter. 
 Fill a tumbler with water quite up to its brim. Lay 
 a flat piece of smooth paper on the surface of the liquid, 
 and then having turned the tumbler as quickly and as 
 steadily as possible topsy-turvy, place it with its rim 
 downwards on a plate. If this manoeuvre be executed 
 with sufficient decision and address, the water does 
 not escape. It is certainly not the paper, however, as 
 I have actually heard contended, which sustains the 
 liquid, a bit more than the car of a balloon, loaded as 
 it is with ballast, and with a miscellaneous freight of 
 weighty articles besides, lifts the balloon from which 
 it is itself suspended. The employment, indeed, of the 
 paper might be dispensed with if the feat were to be 
 performed with extreme dexterity. The sustaining 
 agency is solely the pressure of the air. This gains 
 
childken's toys. 
 
 145 
 
 access to the exposed portion, exclusively, of the sur- 
 face of the liquid when the tumbler is turned upside 
 down, inasmuch as the rest is protected by the glass. 
 Thus the only force to be taken into account is one of 
 upward direction, and it is strong enough, for this is 
 shown by the experiment itself, to bear up a column of 
 water of the tumbler's depth. The paper is of some 
 little use in tending to keep the open surface of the 
 liquid unruffled, and horizontal throughout every por- 
 tion of its whole extent, maintaining for it, as it were, 
 a flat face, so that the supporting power applies itself 
 with a greater evenness of distribution, and conse- 
 quently with a better unity of effect, to the entire area. 
 The delicate conditions of equilibrium thus gain a more 
 favourable chance of preservation. The whole story of 
 the pressure of air, as exerted everywhither within its 
 reach, and as thus tending to leave no vacuum at any 
 spot to which it can gain access, or into which it can 
 propel something else, is, as you see, simplicity itself. 
 
 We have now to inquire how it is that air presses 
 so heavily as it does on all bodies which are exposed 
 to its action. It will be necessary to dwell fully on 
 this subject at whatever risk of being tedious, because 
 unless the power which the weight of the air constitutes, 
 and the effects which it brings about, are thoroughly 
 grasped in conception, not even a thing of such ele- 
 mentary simplicity as a squirt, and still less a pump, or 
 a multitude of common toys and implements, can be 
 really understood. "Trifles light as air" is a saying 
 which contains a certain degree of truth, but which is 
 liable to create misapprehension, because the weight 
 of the atmosphere is in some senses enormous. 
 
 L 
 
146 
 
 children's toys. 
 
 First of all what is air ? It is a mixture of two 
 gases, oxygen and nitrogen, united, but not brought 
 together in equal proportions, since there is a much 
 larger volume of the latter than of the former, but not 
 so much by weight in the compound which represents 
 these two constituents of the union in their married 
 state. Now although oxygen, as being a gas, must, 
 according to the popular idea of such substances, be 
 necessarily something very light, still, it is the fact that 
 many members of the family to which it belongs, are, 
 on the contrary, extremely heavy. Carbonic acid gas, 
 for instance, may be poured from one vessel into 
 another just as if it were water. Oxygen may well be 
 called a heavy substance since it constitutes about half 
 of the material of soils, rocks, and minerals, and a large 
 proportion of the weight of a prize ox, or of a mam- 
 moth gooseberry, is due to its presence. In the case 
 of the ox, as much, perhaps, as about three quarters of 
 his weight may be credited to the oxygen which he 
 bears about his person. 
 
 Now although oxygen is largely diluted with nitro- 
 gen, which is a much lighter element, still it retains its 
 own inherent quality of weightiness, and imports this 
 into the compound of gases which is called air. Nitro- 
 gen, too, although it is no doubt extremely light, still 
 has some weight, and therefore any very great bulk of 
 it would, in the mass, scale up to a high figure. Feathers 
 are not individually heavy, but a legion of them would 
 weigh something, and a featherbed as big as Mont Blanc 
 would be a really ponderous article. 
 
 Now the air rests upon the surface of the whole earth 
 like an enormous featherbed about fifty miles thick. We 
 
children's toys. 
 
 147 
 
 have some grounds for supposing that the atmosphere 
 does not extend to much more than the distance upwards 
 over our heads which has been named, unless in a very 
 attenuated condition, in which it would more properly- 
 pass under some other designation, such as that of 
 ether, since it could then hardly preserve the charac- 
 teristic qualities of the substance which is so familiar 
 to our perceptions as air. We believe, however, that 
 the globe's overcoat of air, properly so called, has no 
 less a thickness than that which has been mentioned. 
 One reason for this opinion is that some years ago a 
 meteor, which was computed to be, at the moment, as 
 much as fifty miles from the earth, was heard to ex- 
 plode. But since sound is, in fact, nothing but ripples 
 of air in motion, the explosion which has been referred 
 to must have been mute if the atmosphere had not 
 extended as far as the spot where it took place. The 
 duration of twilight, also, seems to show, from certain 
 conclusions which are to be drawn from the particular 
 phenomena of refraction which then occur, that the 
 cloud in which the earth, like a deity in the -ZEneid, is 
 enshrined, is of about the depth which has been already 
 stated. But whatever may be the weight of the earth's 
 atmospheric envelope, the heaviness with which it 
 presses on any given spot can be measured as easily as 
 if it were that of a packet of tea. It may interest you 
 to learn, and to be enabled to realise in vivid conception, 
 what kind of amount the actual weight of the atmo- 
 sphere attains at this place where we are assembled. 
 
 To form an idea of its magnitude, suppose that the 
 windows of this room were filled up with brickwork, 
 and the walls carried up to a height of thirty-two feet 
 
148 
 
 children's toys. 
 
 from the floor. And imagine that the large tank into 
 which the room would thus, in effect, have been con- 
 verted were to be filled up to its top with water. 
 There would then, you know, be a very heavy weight 
 of water on the floor as a whole. But this weight 
 would be no more and no less than that with which the 
 air is pressing on it, and on us, at this moment. In 
 other words, a block of water thirty-two feet deep 
 weighs, roughly speaking, as much as a tower of air 
 about fifty miles high, if the area of the base is the 
 same for each. 
 
 Now quicksilver is much heavier than water. If this 
 room were, as has been conceived, made into a tank, and 
 you were to let off the water, and flood it with quicksilver 
 instead, the metallic tide, when it had risen to a height 
 of about thirty inches, would attain to the same weight 
 as that of the water which preceded it, or that of the tall 
 column of air whose base now, in fact, rests upon the floor. 
 The amount of the whole weights of the three several 
 masses of fluid could, of course, be stated offhand, if 
 the dimensions of the base which is common to all of 
 them were ascertained, since it would be the product 
 of 15 lbs. multiplied by the total number of square inches 
 which go to the whole area of the floor. This would be 
 so, because the pressure of the atmosphere, though it 
 varies with the weather, and with sundry other condi- 
 tions, may be taken as being, under ordinary circum- 
 stances, about 15 lbs. to the square inch. Cut a piece of 
 card precisely one inch square, and take 15 lbs. worth of 
 kitchen weights. Lift the latter, and you will find that 
 15 lbs. means something, more especially if you drop 
 the weights on your foot, but this, and no less, is the 
 
childken's toys. 
 
 149 
 
 burden of air which every portion no bigger than the 
 bit of card, of the surface of everything about us has 
 to bear. 
 
 Our bodies, of course, have no immunity, more 
 than anything else, from this pressure, and since we 
 have a great many square inches of surface on our 
 skins, we have to stand altogether a pretty good 
 squeeze. In the case of a grown person of the average 
 size, the atmospheric pressure which he or she has to 
 sustain amounts to the enormous weight of about 14 
 tons. We are entirely unconscious of it, because, since 
 fluids have the property of pressing equally in all 
 directions, if you hold out your hand, although there is 
 a weight of air of, say, perhaps, about 150 lbs., on its 
 back, this is counteracted by the equal and opposite 
 atmospheric force which heaves upwards against the 
 palm. Nor do we feel the clasp of the atmosphere 
 which hugs us in so tight an embrace all round, because 
 this is directly opposed by the no less powerful expan- 
 sive tendency which is exerted by the elastic fluids 
 contained within the body. If these elastic fluids were 
 to cease to act, we should be squashed as flat as pan- 
 cakes in an instant. On the other hand, if the external 
 pressure were to be withdrawn, or much diminished, 
 very serious results would follow. We may step aside 
 from the line of our strict course to notice one or two 
 of such consequences in some slight detail, since they 
 are curious and interesting. 
 
 The weight of the air, as need not be said, is greatest 
 close to the surface of the earth, and becomes less and 
 less as ascent is made from that level. Hence, also, 
 the whole mass of atmosphere becomes gradually more 
 
150 
 
 children's toys. 
 
 and more attenuated in texture as its higher limit is 
 approached. To elucidate this clearly we will take, as 
 before, the case of feathers as an example, since they 
 are the accredited and established representatives of 
 
 light substances. If, then, you had a pile of them, 
 heaped as high as the tip of the spire of Salisbury Cathe- 
 dral, the upper ones would be much less closely packed 
 than those below, because the weight of the former 
 would press down the latter, and condense these into a 
 smaller space than they would have occupied if they had 
 been allowed to lie lightly on one another. Hence it is 
 that when people go up in a balloon, or ascend a high 
 mountain, the pressure of the air on the outside of their 
 bodies diminishes. 
 
 Now we each of us, as you are aware, carry about 
 within ourselves a sort of forcing pump, which acts of 
 its own accord, and which never relaxes its industry for 
 even a single moment until we die. This untiring 
 labourer is the heart. It works very much after the 
 fashion of a pair of bellows. If a pair of bellows were 
 to be filled with a liquid, and the handles were to be 
 then pressed together, the fluid contents would be forced 
 out through the spout. The heart, expanding of its own 
 accord, that is to say without any visible source of action, 
 though its motion is, no doubt, imparted to it from the 
 
children's toys. 
 
 151 
 
 nervous centres, fills itself with liquid. When full, it 
 contracts, again, to all appearance, automatically, and 
 thus forces the blood with which it is charged through 
 the pipes which are called arteries, by constantly re- 
 peated jets, or beats, which we know as a series by the 
 name of the pulse. The tide is driven on beyond the 
 arteries into a labyrinth of tiny hair-like veins called 
 capillaries, which permeate what may be termed the 
 outermost suburbs environing our bodies in all direc- 
 tions. These capillaries are of such delicate structure 
 that they possess but little intrinsic firmness of their 
 own, and they are only enabled by the aid of the con- 
 stricting action with which the atmosphere supports 
 them to control the tide whose impetuosity tries the 
 strength of their texture. When, therefore, this aid is 
 withdrawn, or materially reduced, they get overcharged, 
 and sometimes burst. 
 
 It is necessary to dwell, almost interminably as you 
 may think, on the subject of the pressure which air exerts 
 by its weight, because a very clear idea of the matter is a 
 quite indispensable preliminary, not only to the under- 
 standing of a squirt, but to that, also, of countless other 
 toys and implements. For example, the very simplest 
 and rudest of all playthings, the suckers, consisting of 
 bits of wetted leather, with strings attached to them, with 
 which little boys about the streets raise stones, derive 
 their working power from the pressure of air. Every- 
 body must have seen such a sucker as has been men- 
 tioned in its plebeian form. Identically the same thing 
 appears in a more civilised and elaborate shape, artisti- 
 cally constructed of india rubber and brass, and useful 
 as a self-fixing peg, which may be caused to attach 
 
152 
 
 children's toys. 
 
 itself firmly to a window-pane or any other smooth and 
 flat surface without other support than that of the air. 
 
 The india rubber is of its own natural 
 constitution yielding and flexible, and ac- 
 commodates its face to that of the glass, 
 when applied to it under a little pressure. 
 In the sucker, the leather is wetted, and 
 
 being thus rendered soft, like a plaster, is spread upon 
 a stone. 
 
 Do not suppose that the leather is wetted for the 
 purpose of making it sticky. If it were dry and stiff, 
 it would be hard and unaccommodating, and could not 
 be brought into sufficiently close contact with the 
 stone ; air would then contrive to insinuate itself be- 
 tween the two. In the case of metallic or other sub- 
 stances, the hardness and imperviousness of whose 
 texture is not amenable to moisture, oiling or greasing 
 is resorted to for the purpose of filling up the passages 
 left between two areas of contact through which, if not 
 thus blockaded, air would make its way. Not even the 
 flattest and smoothest plate of metal or glass is, as you 
 will remark, a true mathematical plane, so that the tiny 
 hills and dales which occur throughout its whole ex- 
 tent form so many obstacles to an intimate matrimonial 
 coalition with any other surface. The resistance to 
 complete approach is, of course, doubled when two faces 
 which are thus similarly conditioned, are laid together. 
 
 In the case of the leather the intervention of the 
 water, partly by its softening influence, and partly by fill- 
 ing up, like the oil, any interstices which occur, produces 
 an hermetical, that is to say an airproof, conjunction. 
 This being so, whenever the centre of the sucker is pulled 
 
children's toys. 
 
 153 
 
 a little apart from the stone by means of the string, a 
 vacuum is formed under it. The pressure of the air on 
 the surrounding margin of leather suffices to keep it 
 tightly attached to the stone, so that they may both be 
 raised together by the string without parting company. 
 In the case of the peg referred to just now, the pad of 
 india rubber is placed close against the glass or whatever 
 else it may be, to which it is to cling, and its centre is 
 then drawn back by means of a screw. The air of 
 course behaves as it did to the stone, and squeezes the 
 rim of the pad hard against the surface to which it is 
 applied. 
 
 Nature (which, as being a vague term, is not always 
 a desirable one to use, but is sometimes convenient for 
 describing created things as they are in fact developed 
 and moulded by the surroundings in which they have 
 been set to play their parts), has furnished many ani- 
 mals, and notably the families of limpets, barnacles, and 
 such like creatures, with all the requisite tackle for 
 converting themselves, whenever occasion requires, into 
 living suckers. They are thus enabled, as is neces- 
 sary for their self-preservation and enjoyment, to stick 
 to hard, smooth, and slippery rocks with an obstinacy 
 which checkmates the efforts of most of their many 
 enemies who seek to detach them. 
 
 The effect of the pressure of air is effectively 
 shown by a practical demonstration. The tackle re- 
 quired for the purpose consists of an air pump, and of 
 a hollow iron globe which parts at its waist into two 
 concave hemispheres or cups fitting one another at 
 their edges, which are closely in contact indeed, but 
 without any union whatever other than that of mere 
 
154 
 
 children's toys. 
 
 apposition, so that they will separate again without the 
 least resistance. One of these is pierced by a pipe, 
 through which, when the cups are 
 united, the air which they inclose can 
 be exhausted by means of the air 
 pump. The pipe is furnished with a 
 stopcock by which the entry of air 
 from the outside can be prevented 
 when that within the cups has been 
 withdrawn, so that the globe may still 
 remain empty when disconnected from 
 the pump. It will now be found that 
 the hemispheres, when a vacuum has 
 been formed within them, cannot, owing to the con- 
 verging forces which the atmospheric pressure directs 
 upon them all round, be parted without the exercise of 
 considerable violence. Their mutual and pertinacious 
 embrace is in no degree due to any adhesion of their 
 lips, since on turning the tap of the stopcock, they are 
 found to come asunder without the least reluctance. 
 These cups are familiarly known as the (< Magdeburg 
 hemispheres/' as they were invented by a burgomaster 
 of that city. 
 
 One is reminded by them of the operation of cup- 
 ping, a mode of bloodletting now but infrequently re- 
 sorted to, in which the initial stage of the proceedings 
 is to withdraw some of the air from under a cup applied 
 by its rim to the skin of the patient round the spot where 
 an incision is to be made. The blood which is in the 
 surrounding neighbourhood is driven towards the in- 
 closure, since it is subjected to pressure on all sides 
 except in that quarter. When it has joined that which 
 
children's toys. 
 
 155 
 
 is already on the spot the swollen tide spouts freely from 
 the exit which is opened to it by a slight incision made 
 for the purpose ; just as the winds, according to Virgil's 
 description, escaping from the cave of iEolus, " qua 
 data porta ruunt." A trifling cut has thus, through 
 the contrivance which has been described, the effect 
 of producing a copious flow, which is the object sought 
 to be attained. Anyone who has a curiosity to experi- 
 ence the sensation which attends the preliminary stage 
 of cupping may do so by burning a scrap of paper in 
 a tumbler, and as the flame goes out, pressing the palm 
 of the hand closely over e the rim of the glass. The 
 glass will be found to convert itself into a sucker, and 
 will resist detachment from the hand. The reason of 
 this is that part of the air in the glass was used up by 
 combustion, and the rest was temporarily expanded by 
 heat so as to fill a greater space than that which it now, 
 wheu cool, occupies. A partial vacuum has thus been 
 formed under the hand. 
 
 A similar experiment to that made with the Mag- 
 deburg hemispheres might be shown, in which the air 
 pump would be dispensed with, by substituting for the 
 cups flat slabs of glass or metal pressed close together 
 along one whole surface of each of them. It is not 
 easy to obtain plates of any kind which can in strict- 
 ness be considered as otherwise than ruggedly smooth 
 and mountainously flat, the production of surfaces even 
 approximately true in respect of level being a feat of 
 manufacturing skill of extreme difficulty, to the accom- 
 plishment of which Sir Joseph Whitworth has devoted 
 the highest possible skill and pains. But on pressing 
 together plates which for ordinary purposes may be 
 
156 
 
 children's toys. 
 
 regarded as flat, so that they are brought into close con- 
 tiguity over the whole area of the sides which are in 
 mutual contact, a soft cushion, suggesting to the sense 
 of touch the impression of jelly, or thick but soft oil, 
 will be found to be interposed between them, over 
 which they will readily glide with a sort of floating 
 motion. This is due to the interposition between them 
 of a layer or film of air, the atmosphere having a dis- 
 position to cling with much obstinacy to the surface 
 of everything to which it has once gained access. On 
 squeezing out this fluid cushion by further pressure, 
 the plates are brought to a closer junction, and the 
 weight of the external atmosphere now reaching and 
 acting on their exposed surfaces only, they cannot be 
 dragged asunder without a violent pull. 
 
 This experiment is not so satisfactory for its purpose 
 as that with the cups, since the pressure of the air is not 
 always the only force which is concerned with bringing 
 about the adhesion of two surfaces in contact. Many 
 substances are imbued with a tendency, which varies 
 in strength with the nature of the material which is 
 concerned, but which is sometimes, as in the case of lead, 
 a powerful one, to coalesce with other portions of similar 
 matter, when pieces of them are laid together so closely 
 as to bring the constituent particles of two surfaces 
 which are thus united, into very intimate conjunction. 
 
 The pressure of the atmosphere may be pretty well 
 appraised by trying one's own strength against it. 
 Close a pair of kitchen bellows by pasting an airtight 
 patch over the valve at the side, and stuff up the nose 
 with a cork, so that no air can enter. If you now try 
 to expand them, then the resistance with which the air 
 
children's toys. 
 
 157 
 
 will meet your endeavours to do so will prove a tough 
 antagonist. 
 
 Now that it has been clearly and fully borne in 
 upon your perceptions, as a fact realised in conception, 
 and not as a mere matter of words, that air has consi- 
 derable weight, a great variety of toys and implements 
 whose construction may hitherto, perhaps, have ap- 
 peared to involve some puzzling enigma, will be once 
 for all divested of mystery, and the principle of their 
 action will stand confessed. We are at length, there- 
 fore, in a position of complete advantage for address- 
 ing ourselves to the consideration of engines of a little 
 more complication than squirts, such as pumps, since 
 any power which they might have possessed up to a 
 few minutes ago, to present difficulties, must have been 
 by this time altogether knocked out of them. 
 
 The body of a pump is a hollow tube tenanted, as 
 in the squirt, by a piston, with its rod. The " suction " 
 
158 
 
 children's toys. 
 
 pipe, as it is called, which descends into the liquid which 
 is to be raised, corresponds with the nose of the squirt 
 when snuffling up water. We may demur to the pro- 
 priety of terming the pipe a " suction pipe." The in- 
 accuracy of idea conveyed by the name in question has 
 been already adverted to, but in a somewhat cursory 
 manner, and it is so necessary to avoid the confusing 
 notions, utterly fatal to any understanding of the topics 
 which we are upon, to which the employment of the 
 word " suction " is calculated to lead, that it seems to 
 be a duty to reiterate, as shortly as possible, a caution 
 against the fallacy which the term does its best to create 
 and cherish. For " Suction " seems to imply, or sug- 
 gest, action of some kind or other exerted by the person 
 or thing sucking upon the fluid which is imbibed ox in- 
 haled. The pipe, you must not forget, is absolutely 
 passive as far as relates to the water which is to be raised. 
 It is simply and solely the pressure of the external at- 
 mosphere, and by nothing in the nature of a draught 
 upwards that the water mounts into, and rises within 
 the body of the pump. 
 
 There are two little valves in the ana- 
 tomy of a pump which a squirt does not 
 possess, one of which is at the point of ■ 
 junction of its body with the suction pipe, 
 and the other in the piston. Both these valves are 
 so hinged as to open upwards only. You may not 
 be aware of the fact, but we all, if constructed on the 
 orthodox lines of human physiology, have in our veins 
 a system of little valves, opening, like those in a pump, 
 only one way. Such a phenomenon, however, need ex- 
 cite no surprise as occurring in the persons of improved 
 
children's toys. 
 
 159 
 
 ascidians. The effect of the valves, constituted as they 
 are, is analogous to that of the wicket gates at the en- 
 trance of the Zoological Gardens and elsewhere, which 
 compel the streams of arriving and departing visitors 
 to flow, respectively, in prescribed courses. 
 
 When water is to be raised, the piston is first pushed 
 down to the bottom of the tube, and subsequently 
 lifted. As it rises, a vacuum, as explained just now, 
 is created below it. Thereupon some of the water in 
 the cistern is forced by the pressure of the atmosphere 
 acting on its exposed surface up through the suction 
 pipe into the body of the pump, which it accordingly 
 fills as the piston ascends. The instalment of it which 
 has been raised thus far cannot run back again into the 
 suction pipe because of the lower valve, which only 
 opens upwards, and thus bars any attempt to pass in 
 the downward direction. Such is stroke the first. 
 
 For stroke the second the piston is once more 
 lowered, and as it falls, the water which is in occupa- 
 tion of the body of the pump necessarily pushes its 
 way through the descending valve which opens up- 
 wards on demand. As the piston is again raised, the 
 water resting upon it is lifted, not being able to escape 
 downwards, the designed action of the valve forbidding 
 this. As soon as the water which thus mounts in the 
 body of the pump reaches the level of the spout it natur- 
 ally runs out by that exit, since it is now wholly aban- 
 doned to the control of gravity. The history of the first 
 stroke necessarily repeats itself with every succeeding 
 one. The piston rod, as everybody must have seen, for 
 this part of the apparatus is visible enough, is put 
 in motion by a handle of sufficient length to afford a 
 
160 
 
 children's toys. 
 
 convenient degree of leverage, and is worked with a 
 crank. Such is the common sucking pump. 
 
 If what has been said as to the pressure of the atmo- 
 sphere for any given area being equal to that of the 
 weight of a column of water about 32 feet high has 
 been understood, it will be seen that a common pump 
 cannot lift to a greater altitude than this, so that the 
 range of its usefulness is strictly limited. If, then, a 
 cistern at the top of a house is to be filled from a well, 
 or water to be poured on the roof of a burning building 
 to extinguish a fire, it would be necessary either to 
 employ a series of sucking pumps, one above the other, 
 which would be absurdly inconvenient, or else the ser- 
 vices of a machine possessing capabilities for satisfying 
 the requirements in question must be obtained. Such 
 an implement is found in the force pump. It is just a 
 
 little different from the sucking pump, in two or three 
 points, which are the following. First, its piston con- 
 tains no valve, but is simply a plug, as in a squirt. Also 
 it may be said to have no spout. Instead of this latter 
 
children's toys. 
 
 161 
 
 there is a pipe which opens out of the lower part of the 
 body of the pump, and turns in any direction towards 
 which the water is to be propelled. In this pipe is a 
 valve which is so hinged as only to open upwards. Sup- 
 pose the piston to be at its lowest position. When it 
 is raised, a vacuum is created below it, and the water 
 follows it as it mounts, filling the body of the pump. 
 When the piston descends, the water finding no passage 
 through it, as it does in the case of the suction pump, 
 is driven up the pipe at the side and through the valve 
 therein, which, hung as it is, permits no return. Every 
 valve in a pump is like a certain gate whence " Vesti- 
 gia nulla retrorsum." Thus, by a continued succession 
 of strokes, causing a like series of instalments of water 
 to climb up through the valves, the fluid can be raised 
 in the pipe as high as may be desired. 
 
 Any quantity of water might thus, of course, be 
 lifted to the Cross of St. Paul's from the level of the 
 pavement below, if sufficient power were forthcoming 
 to work the pump. This would be all that could be 
 wanted if St. Paul's were a house, and the require- 
 ment were merely that of filling a cistern on the attic 
 ' floor, but if the building were on fire, and a stream of 
 water were needed for pouring over the dome, the 
 forcing pump, if not equipped with any further appli- 
 ances than those which have been described, would fall 
 far short of the demands which, such an exigency would 
 create. In such a crisis it would be of essential con- 
 sequence to have available some machine capable of 
 throwing water with great force of propulsion, and in 
 an abundant and sustained tide, to any point, or height. 
 Such an engine presents itself in a forcing pump when 
 
 M 
 
162 
 
 children's tots. 
 
 furnished with a trifling and very simple accession to 
 the arrangements by which its work of mere lifting is 
 performed. The additional tackle in question consists 
 merely of a box which a pipe enters but does not com- 
 pletely traverse. The serviceable qualities of the box 
 are entirely due to the elasticity of air, a property which 
 must be fully comprehended before the exact nature 
 of the part which it plays in the instance before us 
 can be understood. Elasticity must first be defined, 
 and when it stands before us represented in terms it 
 may be brought out to view with sharper clearness if 
 light is thrown upon it by a few illustrations. 
 
 Elasticity is the quality through which a body which 
 has been bent, extended, or compressed, reassumes its 
 original posture, shape, or volume, as soon as the force 
 by which its arrangement or figure has been tem- 
 porarily altered ceases to coerce it. Probably all sub- 
 stances in nature have something, however small, of 
 the quality just described. Others possess it in a very 
 high degree, but nothing, so far as we know, is perfectly 
 elastic. A perfectly elastic substance, if the mutual 
 relation of its component particles to one another in 
 point of arrangement, were to be altered by the dilata- 
 tion or compression of its mass, would, when relieved 
 from the disturbing force, re-establish their original 
 disposition with absolute completeness, and would do so 
 with an energy in no degree inferior to that by which 
 the displacement was effected. 
 
 India rubber is a leading example of elasticity, and 
 since a ball of that material is a first favourite among 
 toys, we may take the present opportunity, as being 
 both a legitimate and convenient one, of noticing with 
 
children's toys. 
 
 163 
 
 some little particularity of detail the source whence its 
 attractiveness, which consists in its talent for bounding, 
 is derived. When the ball is dropped on the floor, or 
 ^thrown against a wall, the part of it which strikes the 
 carpet or the bricks, as the case may be, is driven in 
 by the blow. Consequently, the ball loses, for the 
 moment, its symmetrically round figure, and assumes 
 that of a dome bounded in one quarter by a flat base. 
 Immediately, however, that the force of impact has 
 spent itself, and the reaction of the surface on which it 
 was exerted has ceased to squeeze in the ball, the 
 property of india rubber by which it replaces the 
 original boundaries of its mass as often as these are 
 disturbed, is allowed to come into play. Under its 
 influence the flattened portion resumes its convexity, 
 and in so doing, pushes against the surface which it 
 touches. The push, like that of a puntsman, or of a 
 man jumping with a leaping pole, impels the ball 
 smartly from the point of contact, thus causing what 
 is called the rebound. 
 
 If a clean elastic ball be gently laid upon a board, or 
 other smooth surface, which is smeared with wet paint, 
 it will be found, when removed, to have brought away 
 with it a tiny spot, only, of the moist colour, thus show- 
 ing that the contact between itself and the stage on 
 which it rested was confined to a small point only. If 
 the ball be afterwards dropped upon the same surface 
 from a little height above it, or be otherwise brought 
 into more or less sharp collision with it, the area of the 
 spot will be found to extend itself in exact proportion 
 to the energy of impact. This shows by a proof re- 
 corded, as it were, in written characters, that the figure 
 
164 
 
 children's toys. 
 
 of the ball is locally affected by the blow, and to a 
 degree corresponding with the vigour of the encounter, 
 for otherwise contact could only take place at the in- 
 finitely small point where a flat surface and a sphere 
 are capable of touching one another. The shape of the 
 ball must, therefore, it is clear, have been temporarily 
 modified, and lost its character of a perfect sphere. 
 It is also patent at a glance that the original contour 
 of its person has forthwith re-established itself. 
 
 Not long ago, in turning over the leaves of a book 
 on elementary natural philosophy, I noticed an error, 
 which is not an uncommon one, in the definition which 
 was given of elasticity. It was stated that gold, and 
 the material of which spiders' webs are formed, are 
 both of them extremely elastic, inasmuch as they can 
 be drawn out into marvellously long threads without 
 breaking. It is true that the substances in question 
 are extensible to a surprising degree. Gold, moreover, 
 admits of being expanded laterally, as it is eminently 
 malleable, that is to say it may be hammered out into 
 plates which are almost inconceivably thin, surpassing 
 in this respect the scanty smear, amounting to hardly 
 more than an unctuous gleam, which feebly represents 
 butter as spread upon slices of workhouse bread. In- 
 deed gold may be made so attenuated as to lose its 
 opacity, and become translucent. But spiders' webs 
 and gold, so far from being elastic, might be taken as 
 typical examples of just the opposite quality. Elasticity 
 was confused in the book referred to with a different 
 thing, namely, ductility, which means a capability of 
 being led out into threads without losing coherence. 
 To justify a claim to the title of elastic it is not enough 
 
children's toys. 
 
 165 
 
 that a high degree of extension should be tolerated 
 without breaking. Viscous substances, like honey and 
 tar, may be pulled, or allowed to drop into strings, but 
 when so treated they contentedly acquiesce in, and 
 retain their new condition, since they have no innate 
 disposition to concentrate themselves anew into a com- 
 pact mass. It should, perhaps, be observed that 
 matter may be partly viscous, and partly elastic. Ice, 
 for example, possesses elasticity in no inconsiderable 
 degree, but it is also viscous, that is to say, under 
 certain conditions, such as that of the pressure of its 
 own weight, it shares with liquids their mechanical 
 aptitude for running downwards through a channel like 
 water. 
 
 In view of the erroneous notions as to the true 
 meaning of the word elastic, which, as has been men- 
 tioned, are found to exist, and which are promoted by 
 misleading statements made by professed authorities, 
 it may be worth while to point out an instance of a 
 rather different order of the quality in question, namely, 
 that which may be described as the habit of voluntarily 
 resuming an attitude which has been temporarily dis- 
 turbed by some extraneous force. Glass (not the 
 " toughened/' but of the original kind) may be selected 
 as the example now required. When thick, it is brittle 
 and not pliable, that is to say, it will break, but not 
 bend, thus resembling the " nescia flecti 93 spirit of 
 Irish patriotism of which Moore sings in the Irish 
 Melodies. But when spun with threads, or spread out 
 into thin plates, it becomes highly elastic, for these, if 
 bent, or doubled up, will, when the force by which they 
 have been twisted is relaxed, reinstate themselves in 
 
166 
 
 children's toys. 
 
 their original condition of straightness with an indomit- 
 able alacrity such as is not displayed to the same extent, 
 or with the same pertinacity, by any metallic or other 
 substance. The material which forms the substance of 
 glass is of course just the same, with the same inherent 
 qualities, whatever they may be, whether it be in the 
 form of a block, or of thin plates, or of threads. But 
 the mechanical conditions under which it is bent obvi- 
 ously differ with these several states. Steel, within 
 certain limits, is characteristically and exceptionally 
 elastic, as in the case of the blades of Toledo swords. 
 Nor need it be said that steel in the form of watch- 
 spring is elastic, for so to be is the sole end and pur- 
 pose of its existence in that capacity. 
 
 In the elasticity of air we find yet another, and 
 larger, phase of the quality than those which have been 
 reviewed. The essential nature of elasticity is always, 
 it should not be forgotten, the same, and it is only the 
 particular manner in which it displays itself which 
 varies with circumstances. Susceptibility of compres- 
 sion or extension, and automatic self-readjustment as 
 soon as the stress of the external force which has pro- 
 duced disarrangement permits, constitutes the elasticity 
 of air, glass, and steel, alike, and of everything else. 
 In the bending of a watch-spring the particles of steel 
 on the outside of the curve are, of course, temporarily 
 drawn asunder into situations farther apart from one 
 another than such as they naturally occupy, while the 
 atoms of material on the inside are proportionately 
 squeezed together. 
 
 Air has the property of almost unbounded ex- 
 pansibility in all directions, for it penetrates into every 
 
[childeen's toys. 
 
 167 
 
 spot to which it can gain access by any adit, how- 
 ever narrow and tortuous, while at the same time it 
 is ready to shrink under compulsion within extremely 
 ljmited confines. The elasticity of air is, indeed, so 
 dominant a quality of its constitution that any given 
 quantity of our atmosphere cannot be said to have any 
 natural dimensions of its own, but must be taken as 
 accepting and owning such, merely, as are from moment 
 to moment imposed on it by the forces whose combined 
 result determines the amount of extension which it is to 
 possess. It may be too much to say that air is expans- 
 ible or elastic to an absolutely infinite degree. By ex- 
 treme dilatation it may perhaps become disintegrated, 
 that is to say, its constituent atoms may eventually lose 
 both their coherence and their tendency to gregarious 
 arrangement, so that having once parted company very 
 widely, they may be unable of themselves, or indisposed, 
 to resume close association. This happens with india 
 rubber, and with watch-spring, when strained beyond 
 a certain point. The nature and degree of the elasticity 
 of air will be best realised by witnessing some practical 
 effect resulting from it. The air-gun will supply such 
 an illustration as is desired. 
 
 The stock is a hollow tube of strong iron, closed 
 altogether at its butt end, but fitted in front with a 
 valve opening only inwards. The gun is loaded by 
 forcing an excess of air into this hollow stock, say, a 
 dozen or twenty times as much as would in the natural 
 order of things be there. This is done by means of a 
 simple implement called a condenser which will be 
 explained presently. When the air is pushed in, it 
 cannot get out again by reason of the valve which opens 
 
168 
 
 children's toys. 
 
 only inwards, so that the more strenuous the effort 
 made from the inside to open this door, so much the 
 more tightly does it keep shut. When the gun is to 
 be fired, the barrel, which is open at both ends, is 
 screwed on to the stock, so that the bullet, reposing in 
 the breech, is brought close upon the valve which has 
 been mentioned. There is no occasion to describe the 
 precise arrangement of the trigger. It will be enough 
 to say that when pulled it so acts as to throw the little 
 valve open for some fractional part of a second, thus 
 allowing a small instalment of the foremost air which 
 is behind it to escape. The portion thus liberated 
 issues in the form of a sharp puff, and striking full 
 against the hind- quarters of the bullet, propels it from 
 the barrel. The whole proceeding which has been 
 described shows how extremely elastic air is, because, 
 in the first place, it submits to be compressed into a 
 small portion, only, of the space which it had previously 
 occupied, and secondly, it expands again, when per- 
 mitted to do so, with brisk animation and power. 
 
 Experience with an air-gun also shows that the 
 * elasticity of air increases with its density, and varies 
 with it in direct proportion. The trigger, by a suitable 
 adjustment, may be caused to open the valve to any 
 greater or less degree which may be desired, and it will 
 be found by experiment that a small puff given off from 
 air which has been crammed very tightly into the stock 
 is equal in propelling power to a fuller blast when the 
 intensity of compression has been relieved by one or 
 more discharges. 
 
 Many gases resemble air in the capability which 
 they, too, possess of being condensed, and of spontane- 
 
children's toys. 
 
 169 
 
 ous expansion. A good example of the qualities in 
 question js presented by soda water. Soda water is 
 made by the compression of a particular gas called 
 carbonic acid gas. This substance is obtainable from 
 many sources, from chalk among others, and by means 
 of strong pressure it is forced into water, which it occu- 
 pies in the condition of a multitude of tiny bubbles 
 which interpenetrate the body of the liquid. The cork 
 being now driven in, and kept in its place by strings, 
 these take upon themselves the task of maintaining the 
 pressure which has been applied, so that the gas still 
 remains imprisoned, although the particular agency by 
 which it was originally coerced is now suspended. On 
 relaxing the compression, by cutting the strings of the 
 cork so as to allow the force which is acting on its under 
 surface to have its way, the gas, by virtue of its elas- 
 ticity, expands to what we may for convenience term 
 its natural volume. It is this sudden expansion and 
 escape of gas and air which causes the pop and fiz. 
 Soda water has been called " water with a sneeze in it." 
 We have seen that it might be better defined as " gas 
 with a squeeze in it." 
 
 Water has no elasticity at all ; at least none worth 
 speaking of, since under a pressure of 151bs. to the 
 square inch it loses only one 47-millionth part of its 
 volume. If the stock of an air-gun were to be filled 
 with water, fifty steam engines could hardly ram in any 
 more. The receiver might be burst, but the water 
 could not be compelled to retreat into a space ma- 
 terially smaller than that which it is of its own in- 
 clination disposed to occupy. It thus presents a 
 marked contrast to air, which is so elastic that enough 
 
170 
 
 children's toys. 
 
 of it to discharge ten bullets in succession may easily 
 be packed into the small chamber which is constituted 
 by the hollow gun-stock. This brings us to the sub- 
 ject of the instrument by which the gun is 
 charged. The condenser, which is merely 
 in principle the same thing as a pair of bel- 
 lows, is a strong iron tube with a piston 
 fitting it so close as to be airtight. For 
 purposes of convenience and efficiency, the 
 piston, in this case, is made so long in the 
 body that it becomes, in fact, one with its 
 rod, and fits, and fills, the tube like a plug. 
 When the gun is to be charged, one end of 
 the condenser is screwed to the stock. The piston, 
 having been previously drawn out, is now pushed right 
 home to the end of the tube, driving the air there into 
 the stock, whence, by reason of the valve which was 
 described just now, it cannot get back. On the piston 
 being now pulled out again as far as it will go, air once 
 more fills the tube, entering it through a hole made for 
 this purpose in its side. This second tube-full, like 
 its predecessor, is sent to prison in the stock, and the 
 process is repeated as many times as the strength of 
 the operator permits. 
 
 From the severe exertion which a contest with air in 
 forcing it into the stock of an air-gun demands a vivid 
 appreciation is gained of the fact that the atmosphere, 
 though it eludes some of our direct perceptions, is — 
 Hamlet and his " incorporal air " notwithstanding — a 
 " body." Steam, it must be admitted, has a distinct 
 material personality of its own, although, like air, it is 
 utterly invisible. That white vapour which is so familiar 
 
children's toys. 
 
 171 
 
 to us at almost all times and places, is ill reality a fog 
 of minute watery particles caught up and carried by the 
 steam, just as the stream of heated air which ascends 
 from a burning substance bears upwards with it innu- 
 merable tiny atoms of unconsumed fuel forming a cloud 
 which is called smoke. But steam, like air, has never 
 been seen by human eyes. 
 
 This is the right opportunity, while we are still 
 handling an air-gun, for saying a few words about the 
 same weapon in its more innocent form in which it 
 does duty as a toy, and is then known as a pop-gun. 
 An air-gun would appear from its modus operandi to be 
 merely a long and powerful sort of pop-gun. This is 
 partly true. In both cases the pellet, or bullet, or what- 
 ever the missile may be, is, no doubt, impelled by the 
 elastic power of air, but this force does not do business 
 under precisely similar conditions in the two implements 
 respectively. In the air-gun, as has been seen, a maga- 
 zine of compressed air is established in the stock, and 
 allowed to escape in small and sudden gusts. These 
 instalments of captive air leap forth with much vivacity 
 when released from confinement, and expand with an 
 energy which rivals that of exploding gunpowder. In 
 a pop- gun, two pellets are placed, with an interval of 
 space between them, in a hollow tube open at both ends, 
 which they fit so close as to be airtight. When, by 
 means of a stick, the hinder one is pushed towards that 
 which is nearer the muzzle of the pop-gun, the air be- 
 tween the two is compressed, and acts as a strong spring 
 exerting a direct opposition to the thrust of the oper- 
 ator, and striving with equal vigour to force the fore- 
 most pellet forwards. This latter is for some time 
 
172 
 
 children's toys. 
 
 restrained from stirring by friction, which is the impeding 
 power generated by the close contact of the pellet with 
 the interior surface of the tube. As the hindmost pellet 
 is urged onwards, the inclosed air, in proportion to the 
 increasing degree with which it becomes compressed, 
 acquires an augmented expansive potency, and event- 
 ually, overpowering the resistance of friction, dispatches 
 the foremost bullet outwards. 
 
 It would hardly be doing the fair thing by elasticity 
 if we were to dismiss it finally from consideration with- 
 out a more distinct recognition than has yet been ex- 
 pressed of its serviceable character in enabling us to 
 pack up or accumulate stores of mechanical power 
 which may be afterwards drawn upon, or allowed to 
 exert a regulated action of their own, as may best con- 
 duce to the performance of any task requiring some 
 sustained motive agency for its accomplishment. A 
 watch supplies a working diagram illustrative of this 
 remark, since the spring, when coiled by winding, takes 
 in in a moment or so a supply of power which, being 
 allowed to expend itself in an orderly, measured, and 
 slow manner, keeps the works going for a long time. 
 The Mont Cenis tunnel through the Alps was bored 
 by adzes driven by compressed air, which resembles an 
 elephant in its two most prominent characteristics of 
 strength and tractability. For the purpose of the work 
 just referred to, stores of force were accumulated, just 
 as in the case of an air-gun, by squeezing air into closed 
 vessels which thus became ever-ready magazines of 
 power at the disposal of the engineer. Elasticity thus 
 used as a mechanical power is in fact a maid of all 
 work, doing in all directions more multifarious and 
 
children's toys. 
 
 173 
 
 valuable services to the human community than it 
 would be possible to enumerate. 
 
 Force may, of course, be stored in other ways than 
 in the Savings- Bank which elasticity keeps open for its 
 safe custody. The weight of a clock, when raised by 
 winding, is endued with a fund of power which may be 
 called " energy of position/' that is to say, it is gifted 
 with capabilities for work by the mere possession of the 
 situation w T hich it occupies. Dormant energy of this 
 kind is usually called " potential/' to distinguish it from 
 force actually at work, which latter is called " kinetic 
 energy." A reservoir of water upon an eminence is no 
 less truly a reservoir of power, since the fluid possesses 
 in and by its weight a potential energy which it is ready, 
 on demand, to exert. In other words, when it was 
 pumped to its present depository its cistern was filled 
 with energy of gravitation as much as with liquid. Sur- 
 plus force may be also laid up for future use in a flywheel. 
 In this case the deposit of savings of power does not, it 
 is true, form an investment of capital of a more than 
 transitory kind, but it is one which under various states 
 of circumstances has paramount advantages. Notwith- 
 standing the existence of the contrivances which have 
 been mentioned, and of many others, for the storage of 
 power, the facilities which elasticity supplies for the 
 purpose are so great, and in such constant requisition, 
 that they may be said to be indispensable to the neces- 
 sities of mankind, as they certainly are to the arrange- 
 ments of Nature as constituted by the established order 
 of Creation. 
 
 A convivial party of thieves was one evening sit- 
 ting in a public-house, listening to a story which was 
 
174 
 
 childken's toys. 
 
 being told by one of their number, when some constables 
 entered, one of whom, touching the speaker on the 
 shoulder, intimated to him, in policeman's phrase, that 
 he was "wanted." Being "wanted" by the police 
 usually means, as a consequence, a spell of prison, and 
 in the present case the sequel was a term of penal 
 servitude. On being released, after some years of im- 
 prisonment, the convict returned to his ancient haunt 
 at the thieves' public-house where he had been appre- 
 hended, and finding some of his old associates there, 
 resumed the thread of his story which had been so 
 rudely interrupted without further preface than " Well, 
 as I was saying." The perpetual digressions from the 
 main high road of this lecture into the byeways which 
 open along its course perhaps render our journey 
 sometimes a little bewildering to you, as you may find 
 a difficulty, such as the thief s audience may be con- 
 ceived to have felt, in recalling to memory, after a 
 long interval, the exact point whence we diverged. If 
 this discursiveness is to be justified, and I resolutely 
 maintain that it is not only excusable, but right and 
 necessary, it is to be defended on the ground that 
 travellers who visit unknown or unfamiliar districts 
 gain a far more real and thorough acquaintance with 
 the country through which they pass by taking a few 
 steps now and again into the lanes which open off on 
 the right and left of their proper track, and even by 
 wandering into fields clean out of the course which 
 leads to their destination, than is attained by those 
 who, in a strictly methodical, humdrum, and business- 
 like fashion, tramp the highway, not concerning them- 
 selves about the country which lies beyond the hedge 
 
childken's toys. 175 
 
 on either side of their path. And now to resume with 
 the thief's " Well, as I was saying " the thread of a 
 topic which was broken off a long way back. 
 
 In a common force pump, as has been shown, the 
 water is driven up into a pipe, and this may be as short 
 or as long as circumstances may render convenient. 
 In fire engines it is very short, soon ending in a close 
 chamber or box called the air chamber, furnished with 
 a tube, which enters it through its top, but does not 
 traverse its entire length downwards. We will call 
 
 this the exit pipe, because it furnishes an open outlet 
 to the surrounding air. The air chamber may be of 
 any shape : a cylindrical form with a domed top is 
 usually adopted. In the common garden engines for 
 watering, which are nothing else but small fire engines, 
 the air chamber, as can be seen at a glance, is mostly 
 globular, so as to be as compendious as possible, and 
 thus conveniently portable. The water is pumped up 
 into the chamber which is already full of air. Some of 
 the latter is thus displaced, and has to take itself off 
 through the exit pipe. What remains is eventually 
 
176 
 
 children's toys. 
 
 driven by the rising tide into the upper part of the 
 chamber. There, as soon as the liquid has mounted 
 so high as to cover the mouth of the exit pipe, thus 
 barring any farther escape thereby, the inclosed air is, 
 as it were, brought to bay. Being still, however, even 
 in its last place of retreat, squeezed by the flood, which 
 continues to be pumped in as before, it exerts in its 
 turn a very powerful, but equable and sustained pres- 
 sure of reaction on the water below it, forcing it in a 
 copious stream through the exit pipe. To the outside 
 end of this pipe is attached hose, called the " delivery 
 pipe," made of india rubber, or leather, which can be 
 turned so as to spout in any direction which may be re- 
 quired. A fire engine always consists of a pair of forcing 
 
 pumps, both feeding one and the same air chamber, 
 since a fuller head of water, and a more vigorous and 
 better sustained fountain is thus obtained, instead of 
 the somewhat intermittent series of jets which would 
 follow on the strokes of a single piston. Toy fire engines 
 
children's toys. 
 
 177 
 
 which work extremely well are sold by tens of thousands 
 at eighteenpence apiece and upwards. 
 
 Before bidding good-bye to the subjects which we 
 have lately been dealing with as incidental to pumps, it 
 may be mentioned that a working model of an air cham- 
 ber can be made in a minute for nothing by anybody 
 who may care to take the trouble. Fill a 
 common glass phial bottle half full of 
 water. Introduce a pipe (a bit of tobacco 
 pipe will do) through the cork, and push it 
 in far enough to make it descend into the 
 liquid. On putting the bottle over a flame, 
 the water soon begins to shoot in a brisk 
 fountain from the top of the pipe. The 
 reason of this, as is easily discerned, is 
 that when steam is generated, as takes 
 place when the apparatus is heated, the vapour presses, 
 as it comes into being and expands, on the liquid below, 
 squirting it in a lively waterspout through the pipe. 
 The bottle and pipe, as is plain enough, form, con- 
 structionally speaking, an air chamber. This experi- 
 ment may be made even still more easily, but with an 
 effect which, not being of a continuing kind, is hardly 
 so complete as that which has been described, by 
 merely blowing hard down the pipe. The air in the 
 chamber is thus condensed by pressure, and as soon as 
 by the withdrawal of the lips, its elasticity gains free 
 play, it causes a jet of water to leap up through the 
 pipe. 
 
 A proper opportunity has now come for discussing a 
 toy which goes by the name of the Cartesian diver, and 
 which illustrates in a very neat and happy manner 
 
178 children's toys. 
 
 several questions which we have discussed this evening. 
 An hour ago,, perhaps, you might not have found its 
 acquaintance quite so easy to make as it will now prove. 
 The toy displays three things principally ; the elasticity 
 of air, the absence of that quality in water, and the 
 effect of reaction. The thing consists of a 
 tall glass bottle or jar, nearly, but not quite, 
 full of water, and covered at the top with a 
 small sheet of india rubber, which is kept in 
 its place by a bandage of string. Floating 
 in the water is a little glass figure of a man 
 in a dancing attitude. On pressing the india 
 rubber covering with the finger, the figure 
 descends, reascending when the touch is light- 
 ened. If the finger is abruptly removed, the figure 
 spins as it rises. Its behaviour will be found to be in 
 direct and close obedience to the pressure used, since 
 it can be made by the nature of the touch which is 
 applied to sink to any precise depth which may be 
 wished, and either remain at rest or spin there, and it 
 will conform to the order communicated through the 
 tip of the finger by twirling more or less vivaciously 
 or not at all, during its ascent. 
 
 You would probably be well able, after a little reflec- 
 tion on the characteristics of its behaviour, to surmise 
 the principles of its construction. But by lifting one of 
 such figures out of his native element, a short cut may 
 be taken by what is called autopsy, that is to say by 
 ocular inspection of his body, to a knowledge of the 
 influences which govern his actions. The figure, being 
 made of glass, which is heavier than water, would sink, 
 but that it is partly hollow, so that it contains a certain 
 
{jhildken's toys. 
 
 179 
 
 quantity of air. The air, being lighter than water, 
 buoys the figure up, just as a bladder supports a person 
 who cannot swim, or as gas raises a balloon. The 
 figure might with propriety be described as a water 
 balloon. When uncontrolled by any foreign influence, 
 it ascends to the surface of the water, and there stays, 
 poising vertically, as it is caused to do by the weight of 
 its feet which are made heavy with this object. But 
 the bottle, according to one of the specified conditions 
 of its arrangement, is not quite full. There is there- 
 fore a small inclosed precinct, forming a chamber of air, 
 between the surface of the water and the india rubber 
 covering above. When pressure is applied to this 
 covering it yields, because both it and the air below it 
 are elastic. The air in its turn presses like a spring on 
 the surface of the water. But the water is altogether 
 inelastic, so that it transmits the whole of the force 
 which is applied to its surface throughout its own 
 entire mass according to the orthodox practice of fluids. 
 It thus conveys the pressure which is exerted by the 
 finger to the air in the hollow of the glass figure, just 
 as if it were a hard and stiff intermediary such as a 
 piece of stick. The air in the hollow, being elastic, 
 shrinks under compression, and the space whence it 
 recedes is immediately, of course, occupied by the water 
 which is urged forwards at its heels. The whole figure, 
 now that a reduced proportion of its total bulk is made 
 up of light materials, loses buoyancy to a correspond- 
 ing extent, and sinks. With every degree in which the 
 pressure is mitigated, the air confined in the body of the 
 figure reassumes, in consequence of its elasticity, some- 
 thing more of its original volume, and dislodges more 
 
180 
 
 childken's toys. 
 
 and more of the invading water. The figure thus, at 
 last, regains its original specific gravity, that is to say- 
 becomes as buoyant as at first, and mounts once more 
 to the surface. 
 
 Its spinning is simply caused by the action upon 
 it which is induced by the issue of water expelled by 
 the air, as this latter reasserts its territorial rights. 
 The reaction in question is precisely similar in effect 
 to that already described in the case of Barker's Mill, 
 and of other mechanical contrivances which we have 
 had under inspection. It need scarcely be added 
 that the mouth of the hollow from which the water 
 is discharged must so open as that the issue shall take 
 place from, and the consequent reaction tell upon, one 
 side of the figure only, for otherwise there will be no 
 spinning. If the hollow, for example, were to open 
 straight downwards from the crown of the figure's head, 
 or horizontally from the centre of its waistcoat, the 
 arrangement in the first case would impart a faculty 
 for leaping, and in the second for darting backwards 
 like a shrimp, but the whole capacity for executing 
 pirouettes would be lost. 
 
CHAPTER VI. 
 
 HE toy to which we will next pass is one 
 of extreme simplicity but very instructive 
 for all that, and it has a near relation- 
 ship, mechanically speaking, to some of the 
 greatest institutions of the universe. It also figures 
 
 in various engineering devices in almost the very same 
 form as that in which it appears as a child's plaything. 
 
182 
 
 children's toys. 
 
 It consists of a wooden doll fixed to the end of a 
 spindle. The latter is caused to twirl by pulling a 
 string which has been coiled round it, as is done with a 
 top. A loose collar held in the hand supports it, allow- 
 ing it at the same time to spin freely. It is what the 
 toyshop people call self-winding, which means, as they 
 use the phrase, that by a strong impulse adroitly 
 given sufficient momentum may be imparted to the 
 figure to cause it to go on spinning for some short time 
 after the whole length of string which was bound round 
 it has been uncoiled, so that it partially winds itself up 
 again the reverse way, and thus assumes a condition of 
 perfect readiness for a fresh start at a pull by the 
 operator. The bandalore, which is a sort of travelling 
 top, derives such charms as it possesses entirely from 
 its self-winding faculty. The accumulated impetus 
 which it gains in running down the string, aided by a 
 sort of coaxing jerk from the hand of the manipulator, 
 given just at the right juncture, and with a knack 
 which is only to be acquired by experience, imparts to 
 it a capacity for climbing again to the top of its tether. 
 A hoop, or a wheel, allowed to run down an incline will, 
 through the momentum which it acquires in the descent, 
 partially mount an opposite declivity of equal height. 
 
 The figure on the spindle has limbs but loosely 
 hooked to its body so that they may readily assume 
 any postures into which the influence of the spinning 
 may from time to time throw them. It will be found 
 by experiment that the listless inertness with which 
 they hang when the trunk to which they are attached 
 is at rest, is exchanged for a more and more lively and 
 determined tendency to rise at their extremities as 
 
children's toys. 
 
 183 
 
 they swing round with increasing velocity, so that 
 eventually, when travelling with considerable speed, 
 they stand out horizontally like the arms of signposts. 
 Why is this ? Whatever steps we take in search of a 
 reply to this question must, if they are to be effectual 
 and worth their pains, start from a sufficiently early 
 point on the proper route, which may be at the follow- 
 ing well-established position. 
 
 When a body is found to be moving in any other 
 course than that of a straight line, it is of an absolute 
 certainty so doing under the influence of more than 
 one force only. If the matter is considered for a 
 moment, it will be seen that this must of necessity be 
 the case. Nothing can be propelled otherwise than in 
 a straight line, or, as it is usually expressed, otherwise 
 than in a rectilinear direction. A boy cannot throw a 
 stone, or shoot a pea out of a peashooter, so as to hit 
 somebody round a corner. An artilleryman cannot 
 reach the enemy on the other side of an intervening 
 hill by firing cannon balls round the shoulder of it. He 
 may, no doubt, pay his attentions in the quarter where 
 he has ascertained his foe to be by directing them in a 
 calculated track over the top of the hill, so as to drop 
 his favours on the adversary's head on the other side, 
 but in this case he knows that another force besides 
 that which is born of the gunpowder, namely, that of 
 gravity, will inevitably act on the shot with an effect, 
 and in a manner, which can be previously computed, 
 and he arranges accordingly. In other words, the 
 curved path, or trajectory, as it is called, which a ball 
 to be sent over a hill must pursue demands two forces 
 for its production, and although the gunner can only 
 
184 
 
 children's toys. 
 
 set a single one going, he knows that a second of as- 
 certained power and direction will be of itself forth- 
 coming, so that the requisite conditions for organising 
 the whole proceedings are, m fact, at his disposal. The 
 path, therefore, of a bullet or arrow, or any other missile, 
 would always be in a straight line from its commence- 
 ment to its finish if the only force intervening in the 
 matter were the original one of projection. Similarly, 
 when a bowl is trundled, it receives an impulse from 
 the player's hand which is exclusively rectilinear, and 
 cannot be otherwise. Its broad spiral sweep, eventu- 
 ally shrinking into closer and sharper convolutions, is 
 due to the bending of its originally straight course 
 by agencies which are easily to be detected and have 
 been already glanced at. These begin to do business 
 upon it at the very first instant that it becomes free 
 from the absolute control of the player's grasp. 
 
 A body which is itself wheeling in a curve can never- 
 theless only communicate to another object the recti- 
 linear element of the compound of forces to which its 
 own particular movement is due. Witness the behaviour 
 of a cricket ball, which traverses a straight path from 
 wicket to wicket, though delivered by a circular swing 
 from the arm of a roundhand bowler. Witness, too, 
 the conduct of the ball jerked upwards from the trap 
 in the game of trap, bat, and ball. The bowl of the 
 spoon from which the ball is ejected follows, whenever 
 it moves, a path which must of necessity be a fragment, 
 or segment, as it is called, of a circle. The pin divides 
 the spoon into two lengths, which are severally radii of 
 circles, just as if each of them were the spoke of a 
 wheels the pivot the nave, and the path of the bowl the 
 
children's toys. 185 
 
 tire. The ball, however, is projected upwards in a 
 straight line at what is called a tangent to the circle 
 described by the bowl of the spoon. The meaning of 
 
 the expression tangent to a circle is not clear to every- 
 body and may possibly, therefore, want explanation. 
 It is necessary for our present purposes that it should 
 be understood. A. tangent to a circle is a straight line 
 which, to whatever length it may be continued, touches, 
 as its name implies, the circumference of that circle, 
 but without cutting it. The tangent may be said to 
 graze the edge of the circle at the particular point 
 where the two meet. 
 
 Curvilinear motion, therefore, of any kind implies, 
 under all circumstances, that more than one instru- 
 mentality is engaged with its production. Whatever 
 forces may be at work, they are always resolvable into 
 two, one of which strives to carry the moving body 
 along a straight line, and the other to drag it inwards, 
 that is to say towards some point or other on the hollow 
 side of the curve which is described. The indirect 
 contest of these forces is unremittingly sustained along 
 the whole length of the path which is traversed. If, 
 therefore, the balance of antagonisms is by any means 
 
186' childken's toys. 
 
 disturbed through some subtraction from, or addition 
 to, the energy of either of them, the one which remains 
 unimpaired, or which has gained some new accession of 
 vigour, as the case may be, assumes at once a corre- 
 sponding predominance. If the curve in which the 
 moving body travels be such as to form part of a circle, 
 the tendency of the pull inwards must, as will appear 
 on consideration, be towards the centre. Circular 
 movement is taken, for convenience, as the typical 
 example of motion in a curve, and the pull inwards, 
 which, in the particular case of the circle, is towards 
 its centre, lends its descriptive name of centripetal, 
 that is to say centrewards, to the drag on the scooped 
 side of whatever bend is in fact traced. The term fairly 
 enough represents the sort of force which it is intended 
 to describe, and there is no sufficient reason for taking 
 exception to it on the ground of its not being strictly 
 accurate. The word centrifugal, which means flying 
 from the centre, is indictable on the double charge of 
 being both inaccurate and misleading, since it seems to 
 imply the presence of some separate and independent 
 force whose energies are specially and exclusively de- 
 voted to endeavouring to carry 
 the moving body straight away 
 from the central point round 
 which its course sweeps. No 
 such force is, or can be, in ac- 
 tion. What is really at work is 
 a force tending to propel the 
 © moving body straight forwards 
 
 at every point in its career, rather than in a curve. 
 The itinerant object, therefore, when relieved from the 
 
children's toys. 
 
 187 
 
 pull inwards, speeds right forward towards the quarter 
 to which its face, so to speak, happens to be turned at 
 the instant when it is surrendered to the control of the 
 rectilinear impulse alone. 
 
 What occurs is illustrated by the act of slinging a 
 stone. In the incidents to that proceeding, the stone, 
 when it is swung round in order that it may acquire 
 the impulse necessary for taking flight, describes a 
 circle. The cord of the sling represents the centripetal, 
 or detaining, force. The effort on the part of the stone, 
 increasing in intensity with the growth of the momen- 
 tum, and made at every instant during which the 
 whirling in a ring is continued, to get straight away, 
 is the centrifugal force, and the line along which the 
 missile departs, when released, is a tangent to the circle 
 in which it was speeding at the instant of its emanci- 
 pation from control. 
 
 The Earth, in what may be called its aeronautic 
 vogage round the Sun, furnishes an example of the 
 operation of the two contending forces of which we 
 have been speaking. Its orbit, as most people know, 
 is the outcome of two agencies, one of which is the 
 attraction which the sun exercises by its gravity, and 
 the other an impetus, how acquired we can surmise, 
 but do not certainly know, by which our globe has 
 been sent coursing through space. Under the bal- 
 ance which prevails between these two forces, the 
 Earth flits through the Heavens with unvarying regu- 
 larity. Were the Sun, like a woman whose charms 
 are waning, to lose anything of its attractiveness, our 
 orb would forthwith scud right away into some un- 
 known suburb of the Universe. It would not, however, 
 
188 
 
 children's toys. 
 
 do this by the impulse of any force other than one of 
 those of which we have just spoken, but under the 
 conduct of the rectilinear impetus already described, 
 unaltered in itself, and only producing a different result 
 through being now allowed to run riot uncontrolled. 
 Although the term centrifugal is thus seen to be fal- 
 lacious, still, it must, by the rule of Hob son's choice, 
 remain in our service, there being no other expression 
 in current use wherewith to replace it • for "tangential," 
 which is sometimes used, is an unfamiliar word, and 
 not universally understood. The particular effect of 
 the force in question with which we are concerned at 
 the present moment is this, that a body revolving in a 
 circle has always a tendency from the rectilinear ele- 
 ment in its motion to recede from the centre of its orbit. 
 
 To apply what has been said to the toy before us. 
 When it is at rest, as now, the arms of the figure hang 
 idly downwards, since they are under the exclusive 
 control of gravity, which brings their disengaged ends 
 to the lowest position which they are capable of as- 
 suming. When the spindle is twisted, and the figure 
 thus put into whirling motion, two forces are called 
 into being. One of these is centrifugal, being, in fact, 
 the rectilinear impulse communicated by the spinner : 
 the other is centripetal, that is to say, directed towards 
 the centre of motion, and acting as a power of attrac- 
 tion would do in restraining the moving object, or any 
 of its parts, from breaking away altogether. This 
 latter is found in the resistance of the links by which 
 the several limbs of the figure are attached to its body, 
 and thereby prevented from seceding dispersedly from 
 the trunk. The tendency of the rectilinear force is, as 
 
children's toys. 
 
 189 
 
 will be found if the matter is looked into, such as to 
 incite every member of the figure which may be free to 
 move to take up an attitude inclined at right angles to 
 the spindle. Twirl the handle of an umbrella and the 
 ribs will behave in a like manner. In the present case, 
 gravity remaining, as it must do, a constant quantity, 
 that is to say, unaltered in point of strength, it must 
 necessarily be overpowered as soon as any force which 
 opposes it, and which is capable of growth, acquires 
 a preponderating energy. This takes place by de- 
 grees, when the toy is spun, for as the vigour of the cen- 
 trifugal force is progressively raised, the limbs of the 
 figure which are freely surrendered by the looseness of 
 their jointing to the control of the power which becomes 
 more and more completely dominant, rouse themselves 
 at its instigation from their original apathetic posture 
 of hanging idly downwards to that of standing out 
 resolutely stiff and straight from the body to which 
 they belong, like the arms of a sign-post. 
 
 From what has been said it is evident why a mop- 
 head, when it is trundled, takes the shape of a circular 
 flat disc, the reason, of course, being that the ends of 
 its locks of wool all retreat as far as possible from the 
 handle. The locks are prevented from shooting off 
 altogether by being tethered at their inside extrem- 
 ities, but the water which is confined amongst them by 
 certain detaining agencies, as long as they are at rest, 
 is now, by the imperious mastery of the centrifugal 
 force, started from its habitat, and scattered all round 
 in a shower, which, like the mophead, of whose present 
 figure it is in fact an extension, may be described as a 
 flat disc, whose broad surface is at right angles to the 
 
190 
 
 children's toys. 
 
 handle. A familiar illustration of the effect of centri- 
 fugal force when prevailing over gravity is afforded 
 by swinging a vessel full of water round in a circle, 
 like a stone in a sling. The water does not escape, 
 for the same reason that the stone does not drop, what- 
 ever may be the attitudes, topsy turvy, perhaps, among 
 others, which the mode of whirling may cause the vessel 
 to assume at various points in its career. 
 
 Air may be dealt with in the same manner as water 
 trundled from a mop. Parcels and letters used to 
 be sent across London from the Railway Terminus 
 at Euston Square to the General Post Office, a dis- 
 tance of a mile or so, upon tiny trains running through 
 an underground tube along which they were in a 
 great measure wafted by air thrown upon them from 
 behind by centrifugal force. It would not have been 
 convenient, or even possible, in so confined a space 
 to employ a locomotive engine to draw the carriages, 
 so the services of air were enlisted instead, in the man- 
 ner to be now described. The tube was constructed of 
 precisely uniform bore throughout, and with an in- 
 ner surface which was perfectly smooth. The leading 
 carriage was provided with appliances which, although 
 gliding easily over the interior surface of the tube, fitted 
 it with such nicety as to be tolerably airtight, so that 
 the vehicle, when accoutred with these, became in 
 effect, a plug, like the piston of a squirt. The end of 
 the tube, at the further terminus, was closed by a valve, 
 and the air occupying the interspace between this and 
 the front of the train was partially exhausted by an air- 
 pump. For reasons with which you are already familiar 
 the external atmosphere would now exert a strong pro- 
 
children's toys. 
 
 191 
 
 pellent force on the rear of the carriage, sufficient to 
 bear it along. A blast of air thrown off from a wheel 
 by centrifugal force was called in aid to give additional 
 life and decision to the push. 
 
 Such a wheel as has just been spoken of is formed 
 of two solid and circular discs of metal placed parallel 
 to one another so that the surface of one is near to, but 
 does not quite touch, the surface of the other through- 
 out its whole extent. The discs are a little farther 
 withdrawn from one another at their centres than else- 
 where, and round this point they are each perforated 
 with holes. When the hollow wheel which is formed 
 of the discs so adjusted as has been described is set 
 in rapid motion, a strong centrifugal force is im- 
 parted to every portion of it and to the circular slab 
 of air which fills the interior. It has already been 
 mentioned that air clings with a good deal of ob- 
 stinacy to the surfaces of objects with which it is in 
 contact. The discs therefore, instead of slipping 
 through, or past it, as they would do if the property 
 which has just been referred to did not exist, by degrees 
 impart much of their own motion to the contiguous 
 atmosphere which intervenes between them. The air, 
 like the water in the mop, being free to depart, when 
 so minded, or when dragged forth from its retreat, is 
 whirled off from between the open lips of the wheel, 
 and blows in all directions which are continuations in 
 a straight line of its course as it issues forth. The 
 wheel is replenished by other air continually rushing in 
 at the perforations which have been spoken of in the 
 vicinity of the axle. The sustained blast thus gen- 
 erated helped to drive the Lilliputian trains which un- 
 
192 
 
 children's toys. 
 
 unceasingly ran , like a weaver's shuttle, backwards and 
 forwards, from Seymour Street to St. Martin's le 
 Grand. Financially, I believe, the tubular railway 
 which has just been described was not a success, and 
 the undertaking was therefore wound up, but this was 
 not owing to any vice in the mechanical arrangements 
 employed. 
 
 After forming acquaintance with the contrivance 
 by which, as you have seen, air is whirled round, and 
 thus endued with a centrifugal force which converts it 
 into a tiny hurricane, you will find it interesting to look 
 up in any cyclopaedia or book of mechanics, the word 
 " centrifugal," and compare the account which will be 
 found under that heading of a certain sort of pump 
 with that of the pneumatic wheel we have been in- 
 specting. 
 
 In introducing the spindle and figure toy to you I 
 commended it to your attention as affording a clear and 
 direct illustration of a principle on which mechanical 
 appliances of the highest importance are constructed. 
 We have since cleared the ground of any impediments 
 which might have encumbered the course of proof of 
 this statement, and it may now, therefore, be at once and 
 fully verified. The spinning figure is usually one repre- 
 senting a lady. One hears of " giddy girls/' but of all 
 persons whose conduct would seem likely to lay them 
 open to the imputation of giddiness, commend me to a 
 little woman of this kind, spinning violently as she does. 
 Giddy as she may be reasonably assumed to be, yet 
 she attends to serious work, or, in other words, you 
 must have seen this very toy, in almost the precise 
 shape in which we find it in the nursery, made in 
 
children's toys. 
 
 193 
 
 steely playing a part of the highest importance in the 
 management of steam engines. If you have not so 
 noticed it, your habit of seeing things must indeed be 
 a case of " eyes and no eyes." The arrangement which 
 I speak of is prominent to view on almost every station- 
 ary steam-engine, and its appearance is so peculiar 
 that one would think it could scarcely be overlooked, or 
 fail to excite curiosity. The bronze statue which stands 
 on the Holborn Viaduct doing duty, as the label on its 
 base intimates, as an emblematical representation of 
 " Science," holds in its hand one of the implements 
 of which we have been speaking, which is thus taken, 
 (as certain theatrical properties are held to be the 
 garnish which is specially appropriate to particular 
 characters, such as a wand to harlequin, and a hat with 
 metal saints to Louis XI.,) as being a fit and distinctive 
 mark of the impersonification of " Science." 
 
 Its main features consist of an upright spindle, as 
 in the toy under consideration, with two rods suspended 
 therefrom, answering to the arms of the figure. At the 
 ends of these rods are knobs, such as might very well 
 
 o 
 
194 
 
 children's toys. 
 
 represent the fists of the little lady, if they were clenched, 
 only that, as the rods are thin, and the knobs large and 
 heavy, the idea of drumsticks is suggested, by which 
 name, therefore, we will for the future call them. As 
 the engine works, the apparatus, being connected with 
 it by suitable gear, turns round and round, and always 
 with a proportionate degree of speed. It is what is 
 called the governor, and its use and action are as fol- 
 lows. The steam by which a steam engine is set in 
 motion and kept going is generated, of course, in the 
 boiler ; and the activity of the brew which there takes 
 place, is, and must be, irregular. When the fire is hot, 
 it is produced with great rapidity. If the furnace be 
 allowed to get low, the supply of steam is not nearly 
 so quick and plentiful, and the result of this wide and 
 incessant variation, if it were not met by appropriate 
 provisions, would be that the action of the machinery 
 would be very inconveniently fitful and capricious. 
 Sometimes the engine would go a great deal too fast, 
 perhaps dangerously so, and would take a meal of steam 
 serpent-fashion, gobbling and gorging voraciously, 
 and afterwards lapsing for some time into a lan- 
 guid and inert state. The demands, moreover, which 
 are made upon the steam-power by the varying exigen- 
 cies of the work which is to be done sometimes alter 
 largely from moment to moment, and thereby another 
 element of irregularity gains admittance. For the high 
 pitch of energy which may be demanded at some given 
 juncture for the purpose of overcoming, with the calm- 
 ness of assured mastery, the resistance offered by the part 
 of the task which is being, at the moment, discharged, 
 would assume the character of excited vehemence, and 
 
children's toys. 
 
 195 
 
 might perhaps run altogether to riot if it were to be 
 still maintained in undiminished exercise after all oppo- 
 sition had dwindled away to little or nothing. The force, 
 when no longer consumed or checked, would spend itself 
 wholly in the production of inordinate speed. If it 
 rested with the man in charge of the engine to adjust 
 the supply of power to the fluctuating requisitions of 
 each moment, this duty would occupy his close and 
 unremitting attention, and it could not be satisfactorily 
 discharged after all. So the engine is made to regulate 
 for itself its own dietary of steam by the ingenious 
 contrivance which has just been pointed out to you. 
 
 Its action is as follows. The spindle of the governor, 
 an upright rod, is connected by toothed wheels with 
 other parts of the engine, so that it revolves at the 
 exact pace at which the machinery is for the time going. 
 When the engine is conducting itself with proper so- 
 briety, the spindle turns deliberately round and round 
 as if it were an upright spit employed in roasting before 
 a slack fire, and the drum- sticks hang idly down by their 
 own weight. Whenever a better head of steam in the 
 boiler imparts more animation to the proceedings, the 
 rotation of the spindle becomes correspondingly en- 
 livened, and thereupon, for reasons which have been so 
 fully explained, the drum- sticks wake up and begin to 
 open like the blades of a pair of scissors turned down- 
 wards ; and as the speed with which they are whirled 
 augments, they fly more and more decidedly apart. 
 They are connected by rods with a loose collar, slipping 
 with their rise and fall, up and down over the spindle, 
 and controlling, through the intervention of appropriate 
 tackle, the admission of steam from the boiler to the 
 
196 
 
 children's toys. 
 
 cylinder, in which latter place it first becomes an oper- 
 ative power. 
 
 The balls which form the ends of the drum-sticks 
 are purposely made of heavy lumps of metal, so that the 
 centrifugal force, before it can raise them, has to over- 
 come a strong opposition on the part of gravity which 
 strives to hold them down. They do not, therefore, fly 
 upwards on the least provocation so readily as the arms 
 of the toy do. But this, of course, is so by design, and is 
 as it should be, the reason being that serious work is im- 
 posed on the arms of the governor, since the duty rests 
 with them, as has been explained, of moving certain 
 mechanism, a business which in all cases involves the 
 necessity of overcoming the resistance of friction, and 
 sometimes that of gravity also, and they have, moreover, 
 to fulfil this office with an unfailing certainty, smooth- 
 ness, and regularity, such as would not attend the action 
 of insufficient power. It is indispensable, therefore, 
 that they should have momentum, which means energy 
 of movement, and is the product of the weight of the 
 moving body and of its speed, multiplied together. 
 
 To make this clear, it may be as well to give as illus- 
 trations three cases of a high degree of momentum, in 
 the first of which both weight and speed are great, in 
 the second the weight alone, and in the third only the 
 speed, the other multiplier or multiplicand, whichever 
 you like to call it, in each of these two latter instances 
 being very small. A heavy shot thrown from a power- 
 ful gun will be an example of the first kind. Through 
 its huge weight, and extreme rapidity of flight, it 
 acquires the immense momentum which it is its whole 
 business to possess, that is to say, it has an energy 
 
children's toys. 197 
 
 of movement, which, on encountering resistance from 
 the object which is struck, produces a crashing impact. 
 An example of the second mode in which momentum 
 may be composed will be seen in an ironclad drifting 
 lethargically on a slack tide, with a movement which 
 is perhaps not so much as perceptible to the eye. 
 The vessel would be found, however, to be endued 
 with sufficient energy of motion to crack like a nut 
 any smaller craft which were to interpose between 
 it and any fixed obstacle, such as a pier. Here, the 
 vast ponderousness of the burly mass makes up by 
 its composed, and apparently dormant, energy for 
 the absence of speed. The third mode in which a 
 powerful momentum may be constituted will be well 
 exemplified by a sword-fish, a creature which has a body 
 which is but slim, and of no great length, so that it is not 
 at all heavy. The animal however can, with one peremp- 
 tory thrust, dibble a hole, as may be seen by a practical 
 example which is preserved in the Museum of the College 
 of Surgeons in Lincoln's Inn Fields, through a vessel's 
 copper sheathing and a skin of oak scarcely, if at all, less 
 hard than the metal, in a manner which must be seen to 
 be believed. The weight of the fish being so incon- 
 siderable, his charge must be like a flash of lightning 
 for speed, as may be read in the extraordinary record 
 which its effects, as exhibited, present. 
 
 Now the arms of the spinning figure in the toy 
 might, no doubt, according to the formula which was 
 given just now, be caused to possess as high a degree of 
 momentum as those of the governor of a steam engine, 
 if their speed of revolution were to be sufficiently 
 raised to compensate for their want of weight. But 
 
198 
 
 children's toys. 
 
 it would be difficult to endue them with any such 
 headlong rapidity of motion as would be necessary to 
 fulfil such a condition as this, and their behaviour, if 
 their whirl were thus to become a whiz, would lack the 
 staid sedateness which should belong to capable, yet 
 gentle, mechanical agencies. The momentum which 
 the drum-sticks with their heavy ends acquire with and 
 by quick motion may be realised in conception when 
 the curious but well-established fact is adverted to that 
 massive iron wheels, when set to spin with extreme 
 rapidity, have been known to fly asunder. In such a case 
 as that, the centrifugal force and the weight of metal 
 being both very large, and, consequently, the product 
 of the two, when multiplied together, enormous, the 
 momentum acquired by the outside rim, or periphery, 
 as it is called, of the wheel becomes so powerful and 
 violent (the energy of motion being, of course, greatest 
 in that quarter), that it has been sometimes known, 
 as has been stated, to tear that portion away, and hurl 
 it to a distance. A similar occurrence has not infre- 
 quently happened with large grindstones. Some of 
 you may probably have seen the process of stamping 
 or cutting holes in metal by a die, or punch, as the case 
 may be, brought down upon the surface which is to be 
 operated on by means of a screw descending vertically 
 through a fixed collar. The screw, in such cases, is 
 worked by a cross bar, forming in effect two levers, and 
 the latter is rendered capable of being endued with the 
 momentum which is necessary for executing the work 
 to be done with proper decision by being furnished at 
 the end of either arm with a heavy metal ball. These 
 balls are set swinging round by the operator, and the 
 
CHILDEEN's TOYS. 199 
 
 blow which by their momentum they deliver through 
 the screw at the point of impact upon the metal which 
 is to be dealt with, is an effective one. 
 
 It may not be out of place to mention here that 
 another self-acting regulator of machinery is sometimes 
 used in cases where the governorwould be unsuitable, as, 
 for example, when the motive power, or " prime mover," 
 as it is called, is a weight or spring, so that, consequently, 
 there is no steam to cut off. The contrivance in ques- 
 tion consists simply of two or more vanes, or fans, set 
 upon an upright spindle with their surfaces vertical so 
 as to be flat to the air when in motion. The spindle, 
 as in the case of the governor, shares, through some 
 appropriate arrangement, the motion of the machinery 
 to which it is attached, so that as it revolves the fans 
 encounter from the air a resistance whose energy in- 
 creases in a multiplied proportion to the speed of mo- 
 tion. This statement will be accepted as true when it 
 is remembered that if the fact were otherwise raindrops 
 (not to speak of hailstones), as the accelerating power 
 of gravity is exerted on them, and with constantly aug- 
 mented effect throughout their whole course of descent, 
 would eventually acquire so extreme a degree of mo- 
 mentum as to dash themselves on the earth with the 
 force of shot from a gun. Whenever, therefore, the 
 revolution of the fans becomes unduly accelerated, the 
 opposition of the air is roused to correspondingly vigor- 
 ous action, and the latter progresses in strength by 
 steps which may be said to outpace any advances of its 
 exciting cause, thus responding effectually to the need 
 of check by which it has been called forth. A fan 
 regulator is of more complete efficiency than a governor 
 
200 
 
 children's toys. 
 
 in one respect, inasmuch as it combats in its own per- 
 son forces running to riot, but it does not, like the 
 governor, cut off, contract, or economise, superfluous 
 impulse. 
 
 A simple proof of the fact referred to just now that 
 the resistance which a fluid such as air or water opposes 
 to motion multiplies with increase of speed, and (for 
 this is only, of course, another way of stating the same 
 proposition) falls by a proportionately rapid scale with 
 its diminution, may be noticed at any dock or port. 
 Large ships may be seen towed from one station to an- 
 other by a rope from a small boat, which latter is rowed, 
 perhaps, by no more than a couple of men. The water 
 offers so mild a resistance to the very slow glide, which 
 is all that is wanted or desirable in a confined space, 
 that the insignificant force which is employed suffices 
 to draw a huge mass. 
 
 There is another contrivance which should be men- 
 tioned as acting on the same principle as the spinning 
 doll, which is employed for insuring the safety of men 
 who work in mines when descending or ascending deep 
 shafts to and from their scene of labour. The rope by 
 which the basket used for their conveyance is lifted or 
 let down is coiled round a revolving drum like thread 
 on a reel. To the axle of this drum, or to some part of 
 the machinery immediately connected with it, arms are 
 attached, which are furnished at their outer extremities 
 with grappling hooks. The connection of the arms 
 with the axle is by a loose joint, which enables them to 
 swing quite freely. As long as the drum revolves only 
 at the staid pace which is safe and proper, the arms 
 hang passively downwards, but if any slip of the gear- 
 
children's toys. 
 
 201 
 
 ing of the machinery should occur, and the rope begin 
 to run out with undue speed, the arms, extending them- 
 selves through swinging upwards by centrifugal force, 
 catch with their grappling hooks fixed iron rings, and 
 the machinery is thus instantly brought to a standstill. 
 The rings of course are so situated as to be just beyond 
 the circle described by the hooks when the arms are not 
 extended. They are placed however in such immediate 
 vicinity to the orbit of the hooks as to catch them at the 
 very first instant when this becomes enlarged, that is 
 to say at the earliest moment when some slight exten- 
 sion of the arms is both the result and the proof of the 
 machinery having broken from control. It is of course 
 of extreme importance at such a crisis as this that the 
 running out of the rope shall be at once arrested, since 
 the weight which is no longer properly sustained 
 gathers increased momentum, more violent and danger- 
 ous in itself, and more difficult to curb, with every ad- 
 ditional inch through which it is permitted to fall. The 
 safety catch which has been mentioned was formerly* 
 used, and occasionally is so still, but more handy and 
 compendious devices are now available for the same 
 purpose. 
 
 The spinning toy which we have been discussing 
 is, as you now see, almost more than a type or shadow 
 of a very important mechanical contrivance in constant 
 use, namely, the governor, being in truth, as far as it 
 goes, almost the identical thing itself. It only falls 
 short of it in respect of certain additions which do not 
 alter the nature of the source of action, though they 
 render the plaything a grave and important function- 
 ary. The principle of the governor is also concerned, 
 
202 
 
 children's toys. 
 
 as was observed in introducing the subject, with some 
 of the greatest features of Creation. This proposition 
 will be established if the behaviour of the doll, when 
 spun, be shown to be due to, and to illustrate, the very- 
 same agency as that by which many, if not all, of the 
 worlds which people the universe were formed, shaped, 
 and were, and still are, ordered in their goings. A 
 perception of this truth must be gained by reverting 
 once more to the precise effect which spinning produces 
 upon the toy. The centrifugal force which is generated 
 by the movement in question possesses, as has been 
 seen, a tendency to carry the arms and legs of the doll 
 as far away as possible from the spindle on which they 
 are spun, or, from what is called the axis of rotation. 
 This is visibly observed to be true of as many portions 
 of the lady's body as are capable, through swinging 
 freely from a point of loose attachment, of altering 
 their position, and if the experiment were to be made, 
 the same thing would be found to hold true, as indeed 
 we know must be the case, of the whole figure. If, 
 therefore, her person were made of butter, or clay, or 
 of any other substance tenacious enough to hold to- 
 gether as one mass in spite of the efforts of a force of 
 moderate intensity to tear it asunder, and if it were 
 yet at the same time of a texture sufficiently yielding 
 to allow the exterior contour of its form to be moulded 
 to any shape which the result of the struggle between 
 the disrupting agency in question and its own cohe- 
 siveness would naturally lead it to assume, and if the 
 toy so constituted were to be set spinning, the follow- 
 ing course of events would be witnessed. For reasons 
 which a little consideration will disclose, the figure 
 
children's toys. 
 
 203 
 
 would in the first place betray an inclination to corpu- 
 lence about the waist, and this disposition would pro- 
 nounce itself with constantly increasing emphasis. The 
 same tendency continuing to predominate, substance 
 would be drawn towards the middle from the limbs, so 
 that they would be first depleted, and eventually ab- 
 sorbed altogether, being taken up for filling the ever- 
 expanding girth about the hips. The figure would thus 
 at last become all waist, that is to say, a ball. If the 
 spinning were to be still continued, and with increased 
 velocity, the figure would become by succeeding trans- 
 formations, first, in point of shape, an orange, then 
 something flatter like two saucers joined at their edges, 
 and, after that, a mere thin disc, till eventually even 
 its power of consistence as a whole would be overcome, 
 and its various component atoms would part company, 
 each flying off on its own separate and independent 
 course, like the drops from the head of a trundled mop. 
 
 There is very good reason for believing that the 
 Earth owes its existence as a mass possessing a distinct 
 individuality of its own to having been shot off in the 
 condition of a small whiff of haze from some larger 
 cloud of matter at the juncture when the complete 
 coherence of the main body of vapour was overcome 
 by centrifugal force. Whether this be so or not, it is 
 certain that it acquired its existing shape, which, as 
 you probably know, is orange-like, or what would be 
 technically called "an oblate spheroid/' through the 
 operation of the very same force which causes this toy 
 when spinning to extend its arms. The Earth, which 
 we believe to have been at first gaseous in composition, 
 and afterwards liquid, now consists, as we know, of an 
 
204 
 
 childeen's toys. 
 
 assemblage of varied, but substantial materials packed 
 inside the thin crust on which we live. If the North 
 and South Poles were the two ends respectively of a 
 real pole on which the globe revolved as on a spit, the 
 inevitable tendency of a more or less viscid lump, such 
 as Mother Earth was in her juvenile days, would be, 
 under such conditions as have been imagined, to bulge 
 out at the waist, that is to say at the Equator, and to 
 retreat into itself at the poles. The Earth does, as a 
 matter of fact, spin round an axis of motion whose 
 position coincides with that of a straight line drawn 
 from pole to pole. 
 
 If any Arctic Expedition to be hereafter under- 
 taken for investigating what may be called the crown 
 of the world's head ever reaches that goal and end of 
 its journey, it will not, according to popular anticipa- 
 tion, find the North Pole sticking up out of the snow 
 in order to form a flagstaff for the Union Jack, nor, 
 it may be added, will the climate be found genial, 
 although a position at the back of the North Wind 
 having been gained, a haven will have been reached 
 which Boreas by his very nature is precluded from 
 touching otherwise than^with the extreme edge of his 
 coat-tails before making a start to chill and torment 
 the world down South. But a curious phenomenon 
 will be observable, which will be quite intelligible to 
 any one who understands this toy, for one explanation 
 elucidates both. The prodigy in question will be the 
 progressive increase in weight of everybody and every- 
 thing as higher and higher latitudes are attained. 27. g. 
 a packet of tea weighing a cwt. in London will gain 
 towards half a pound. Pendulum clocks, also, will be 
 
children's toys. 
 
 205 
 
 found to go quicker. The reasons why these things 
 will be so are not far to seek for any one who may care 
 to stir in quest of them. But to diverge into them at 
 this moment would render our track too much of a zig- 
 zag, and we have already, perhaps, run off the rails of 
 our main line into too many of such sidings. In ac- 
 cordance however with the principle which is contended 
 for as being certainly and in every sense true, that 
 nothing is to be thoroughly understood until viewed in 
 all its bearings, so that these ought to be, as far as 
 possible, even if it be but cursorily, indicated, it is 
 proper to suggest, without minutely explaining, two 
 interesting experiments which may be made by anyone 
 in private, and which illustrate the question which we 
 were discussing just now as to how the Earth should 
 be taken to have come by its actual figure. 
 
 The first of these is a common way of showing only 
 how our globe at some period or other of its history, 
 perhaps at its birth, or perhaps (for this has been shown 
 to be possible) not till a later date in its existence, ac- 
 quired the peculiar and well-known contour of its mass. 
 
 The apparatus required consists of a hoop, made of some 
 heavy, but elastic, material, and placed in a vertical 
 
206 
 
 children's toys. 
 
 position. It is fixed in that attitude by being fastened 
 at its lowest point to an upright rod. The rod passes 
 freely through an open hole, or collar, at the top of the 
 band which forms the periphery of the hoop, and it is 
 equipped with suitable tackle, of which a winch and 
 some multiplying wheels are the main features, by which 
 a rapid motion round its own axis, that is to say round 
 the central line of its length, can be imparted to it. 
 When it is made to rotate, and with it, necessarily, the 
 hoop, since they are joined together, as has been said, 
 at one point, the latter will be found, as would be ex- 
 pected from the considerations which have lately be- 
 come familiar to us, to lose its circular form and assume 
 an oval one to a degree precisely corresponding with 
 the rate at which it spins, that is to say, with the 
 amount of centrifugal force which its constituent par- 
 ticles acquire. Its top being enabled to descend freely 
 down the rod, which it merely encompasses, without 
 clasping, the hoop squats, as it were, more and more, 
 the faster it spins. The demonstration which this ex- 
 periment affords is sufficient for its one purpose, and 
 its bearing on the history of our globe's structure is 
 obvious. It may here be mentioned that the deviation 
 of the Earth's figure from true sphericity, that is to 
 say the extent to which our orb departs from the cha- 
 racter of a completely round ball, is as follows. At the 
 Equator its diameter is about 7935 miles, and it is 
 about 35 miles less at the Poles. 
 
 The second and more delicate experiment which 
 was recommended to you, while supporting, and with 
 no less decision, the same conclusion as that which is 
 established by the behaviour of the revolving hoop, is 
 
children's toys. 207 
 
 far more suggestive and full of instruction. It involves 
 however, so much delicacy of manipulation that it 
 could not easily be shown to a large body of spectators, 
 so that it must be made the subject of private enter- 
 prise. It is to be executed as follows. A globule of 
 oil is caused to float in the centre of a mass of trans- 
 parent liquid. The adjustment of the conditions under 
 which the necessary equilibrium of the fluids concerned 
 will be procured may be brought about by diluting 
 spirits of wine, which are lighter than oil, with water, 
 which is heavier. The right proportions will be readily 
 ascertainable by experiment. The mixture must be 
 caused to have the same specific gravity as that of the 
 oil which is used. In other words, such a compound 
 of lighter and heavier ingredients is to be made as that 
 any given quantity of the liquor thus brewed would, if 
 it were put into one of the saucers of a pair of scales, 
 exactly balance in weight an equal bulk of the oil placed 
 in the other saucer. The globule of oil, when the ad- 
 justment which has been described has been accom- 
 plished, will float in the prepared fluid without any 
 disposition either to rise or sink in it, so that by a 
 little gentle management it may be persuaded to take 
 up and retain any desired position within the body of 
 the liquid by which it is enveloped. 
 
 If a straight piece of wire be now made to descend 
 through the middle of the globule, so as to form, in 
 effect, a spindle, and be then steadily and delicately 
 twisted round by the fingers or by some other suitable 
 agency, its motion will by degrees communicate itself 
 to the sphere of oil, which may thus be brought to 
 rotate on its own axis. As its speed of revolution 
 
208 
 
 children's toys. 
 
 augments, the. globule will pass through the successive 
 phases of a spheroidal figure of a flatter and flatter 
 character into a thin disc. Ultimately, if the pro- 
 gressive rate of the whirling motion be continued, a 
 phenomenon, which the experiment with the hoop 
 stops short of, will be presented by a flat ring being 
 thrown off, so as to form a sort of halo, which, although 
 it preserves no contact with the edge of the disc from 
 which it will have disengaged itself, and therefore, 
 keeping up no communication with the wire axis, its 
 hitherto source of motion, will still continue to spin 
 round the nucleus of oil, and at the same pace with it. 
 
 Here is manifested in a striking form the effect 
 of centrifugal force when acting on a plastic mass of 
 matter such as the Earth certainly was when it first 
 took a definite and permanent form. The action of the 
 force in moulding a ductile substance into various 
 shapes, which are severally the results, as also the 
 registers, of its successive stages of energy, is in the 
 first place witnessed, and its disruptive power, when 
 its intensity reaches a certain height, is subsequently 
 displayed. We have in evidence before us, in the 
 experiment which has been described, the principle of 
 the Governor, as seen when at work in a wider sphere 
 than in a steam engine, or in the toy, arranging the 
 constitution of the universe, and conducting some of 
 the biggest processes of Nature. We see at the same 
 time why, as was stated just now, it occasionally 
 happens that a grindstone will fling itself to pieces 
 when its rapidity of spin becomes extreme, and we 
 cease to wonder how it can be that a flywheel, albeit 
 constructed of strong and sound iron, is liable under 
 
children's toys. 
 
 209 
 
 similar conditions to a like disaster. And last, but not 
 least, we are confident that we are reading, as surely 
 as though, it were written in clear characters in an 
 authentic record, the true history of the birth and con- 
 tinued existence of Saturn's Eing. 
 
 A working diagram of the different phases which a 
 plastic mass assumes when set to rotate may be seen 
 any day at a pottery, where rough lumps of soft clay are 
 by this means quickly, neatly, and effectively converted 
 into thin crusts, as dough is by a rolling pin, from which 
 condition they readily pass at the touch of the workman 
 into vessels of any desired forms. The "potter's wheel" 
 is a familiar name even to those who have never seen the 
 process just described, or troubled themselves to im- 
 agine what its character may be. Glass, which, when 
 fused, is of a glutinous consistency, is spread like 
 potter's clay into thin sheets, suitable for windows and 
 other multifarious uses, simply by being taken up in 
 lumps from the melting furnace at the end of a bar, and 
 then whirled round. 
 
 It may be mentioned that the particular arrange- 
 ment and sequence in which the concentric layers of 
 matter which constitute the substance of the Earth 
 as a whole are stowed within its figure was dictated by 
 the same forces as those which shaped its globular form. 
 The combined effect of the agencies which have been 
 mentioned would be, speaking very roughly, to build up 
 the fabric of the Earth by successive deposits superim- 
 posed one on another like the coats of an onion, the loosest 
 and lightest outside, and the density and weight of the 
 other members of the series increasing up to the centre. 
 There are, as need scarcely be said, no such separate and 
 
 p 
 
210 
 
 children's toys. 
 
 distinct beds of material, but the whole mass, as we have 
 full reason to believe, gradually thickens from the ex- 
 terior surface inwards. The idea of layers was merely 
 suggested for the purpose of imparting the notion, 
 which is a true one, that if the closeness of texture 
 of the Earth's body were to be appraised by reducing 
 the globe by means of stripping from its surface suc- 
 cessive envelopes of matter all of one given depth, these 
 spheroidal crusts, or shells, whether taken individually 
 or as a series, would be found to become more and 
 more dense in a course of regular progression from the 
 outside towards the centre. This state of things which 
 was theoretically to be expected has been verified, 
 through experiments made by means of the pendulum, 
 as that which actually prevails, and it has been found 
 that the innermost strata have a density which is at 
 least four times as great as that of the outer coat on 
 which we live. 
 
CHAPTER VII. 
 
 E will now turn to our dear old friend the 
 common peashooter. If the sources of its 
 attraction for boys were to be analysed, 
 they would probably be found to reside, 
 like those of partridge shooting, partly in being con- 
 nected with the predatory instincts which are indi- 
 genous in human nature, and partly in the satisfaction 
 which attends the prosperous accomplishment of any 
 feat requiring precision and adroitness of execution. 
 But in the view of boys with healthily constituted dis- 
 positions an additional joy belongs to pea shooting in 
 that it can be made a not inconsiderable means of mis- 
 chief and annoyance, the pea being capable of being 
 driven with so much force as to damage an eye or 
 break a pane of glass. A peashooter in its magnified 
 form, when it becomes what is called a blow-tube, may 
 be used for killing small birds, or for shooting darts 
 at a target. There is but little, but still just something, 
 which is worth a moment's notice In the action of a 
 peashooter. 
 
 Take a pea, and try to shoot it by your breath, 
 but without a tube. It will travel no distance at all, 
 
212 
 
 children's toys. 
 
 not even if you blow as King Lear adjured the winds 
 to do " till you crack your cheeks/' or like the frog 
 in the fable, as given by Horace, " si te ruperis.*" 
 Why is the force employed under such circumstances 
 so void of effect ? A glance at a river or brook run- 
 ning into the sea, or into any large tract of water, will 
 supply the answer to this question. A river which, as 
 long as it is confined within a narrow channel, possesses 
 a certain degree of energy of flow, loses all its power 
 of progress, though without encountering any rigid ob- 
 stacle, directly it enters a lake or the sea. For it then 
 dissipates its forces, spending them on an inert mass 
 of water, which calmly and silently absorbs the stream 
 and its impulse, its body and life, together. A pre- 
 cisely similar fate befalls the gush of air which issues 
 from the lips when a puff is given. In the absence of 
 any suitable contrivance for preserving to the outrush 
 of breath its character of a stream, the current wastes 
 its power in communicating to the atmosphere in its 
 immediate vicinity an impulse which is weak through 
 the infinite subdivision of its energy exerted as this is 
 in all sorts of directions. When, however, a blast is 
 delivered into a peashooter, the current of air is set 
 going along one particular line only, and- it is kept 
 strictly to business, so that it rushes through the tube 
 like a torrent through a gorge. Its impetus, unlike 
 the sustained force of a stream, is a hasty spasm of force 
 which is soon exhausted, and even if it survives so long 
 as to reach the muzzle of the peashooter, it is then, of 
 course, at once and finally squandered abroad. But by 
 that time it has communicated a lively force of pro- 
 jection to the pea. The increase of mechanical potency 
 
children's toys. 
 
 213 
 
 winch impetus acquires by transference from a fluid 
 such as the air to a rigid body such as the pea should 
 be noted, and the reasons why this is so should be con- 
 sidered. The clear perception of these matters which is 
 easily to be gained by a trifling exercise of thought is 
 necessary to the understanding of the main point in the 
 action of a peashooter, to wit, the effective dispatch of 
 the pea. 
 
 The barrel of a gun is obviously, as far as the 
 principle of its design is concerned, the same thing as 
 a peashooter. A bullet, placed upon an unconfined 
 heap of gunpowder, which is afterwards fired, will be 
 carried but a very little way, for although an abundance 
 of power is generated, this is directed into no set chan- 
 nel ; it is " vis consili expers," and is thus void of any 
 business-like effect. Only some fractional part of it is 
 exerted upon the bullet. On contracting the field of 
 the powder's action by a tube, that is to say, by a gun 
 barrel, a very different result is obtained. 
 
CHAPTER VIII. 
 
 E will now turn to balls, which may claim to 
 be not only toys, but something more. 
 Marbles, billiards, tennis, cricket, football, 
 and a hundred other pastimes are, as every- 
 body knows, nothing but ball-play in one form or 
 another. No games have been so universally popular, 
 or through so many past ages, as those with balls. 
 The word "ages" is advisedly used. Balls were 
 favourite instruments of amusement in the time of 
 Plato, that is to say about 2300 years ago, and the 
 description which he gives in " Phsodo of the kinds 
 which seem to have been the most popular in his day 
 applies with curious exactitude to some of the varieties 
 which are still common, and of which you may always 
 see basketfuls on sale in the Lowther Arcade, and at 
 every toyshop. The name " Pall Mall," marking, as it 
 does, the place where a certain game of ball known by 
 this title used to be played, is a standing testimony to 
 the favour with which amusements of this kind were 
 formerly regarded. There is nothing new under the 
 sun, and Croquet, which came into vogue a few years 
 ago, to be the fashionable craze for a while, and be 
 
childeen's toys. 
 
 215 
 
 then discarded for pastimes of later invention, had some 
 points, as it would seem, of resemblance to " raHmaU," 
 since the tackle used in both cases appears to have been 
 of the same order. The balls and long-handled mallets 
 which constitute the stock in trade for Croquet have 
 their u analogues," or items with which they corre- 
 spond, in the implements used in Pallmall, as is shown 
 by the etymology of the latter name. For " pall " is 
 merely the Latin "pila," which reappears in modern 
 Italian as "palla," a ball, and mall is the Latin "mal- 
 leus," Italian " maglia," French "maille," and English 
 " mallet," the hammer by which the ball is struck. It 
 would take a long time to give any succinct account of 
 the various games with balls which have been in vogue 
 at one period or another. We can only give attention 
 at this moment to some of the mechanical principles by 
 which the conduct of balls is regulated. 
 
 Suppose an elastic ball to be thrown against a wall. 
 It comes straight back. So, also, does it come straight 
 back if it is dropped perpendicularly on the floor. But 
 if it strikes the wall or floor in some other manner 
 than that which we have called straight, that is to say 
 otherwise than at a right angle, it retreats from the 
 point of impact in a course which is precisely as oblique 
 as that of its previous approach. Why this is so should 
 be ascertained. 
 
 Suppose, then, A to be a wall, and that a ball is 
 
 thrown against it 
 ball is utterly in- 
 
 from any direction. If the 
 elastic, its motion will be ar- 
 rested by the surface of the bricks, and it will tumble 
 dead to the ground at the foot of the wall, just as a 
 pat of butter or a lump of clay would do if thrown 
 
216 
 
 childeen's toys. 
 
 in the same manner. There is a graphic picture in 
 Tennyson of seabirds which flying against a lighthouse 
 in a storm "Dash themselves dead" — suddenness of 
 impact and consequent and immediate destruction of 
 life and motion are here vividly presented to the ear as 
 well as to the eye. If the ball be more or less elastic, 
 and strike the wall flat on its face, it will return after 
 the collision towards the point whence it started. If it 
 be highly elastic, it will come back with a force almost 
 equal to that of its projection, or, in more popular 
 language, nearly as hard as it went. If its elasticity be 
 but feeble, then the impetus with which it is dispatched 
 on its return journey will be correspondingly languid, 
 so much so, perhaps, as to die out altogether at a more 
 or less early stage on the homeward route. 
 
 Now suppose the ball to be perfectly elastic, and 
 to be thrown so as to hit the wall obliquely as it would 
 do if it travelled along a line such, for example, as c n. 
 
 F Whither will it betake itself on its 
 rebound ? The parallelogram of 
 forces will supply the answer to this, 
 E as to so many previous questions 
 to which we have sought replies, 
 c Draw d e from d at right angles to A b, 
 and complete the parallelogram bced. Then c i) will 
 be the diagonal, and a force represented in power 
 and direction by c d will at the point n be equivalent 
 to the resultant of the two forces b d and e d. The 
 ball therefore when at its point of impact d may be 
 taken to be inspired by the two forces b d and e d. The 
 blow against the wall is a coup de grace to the force 
 E D, killing it outright, since it can carry the ball no 
 
children's toys. 
 
 217 
 
 further. Bui, as was shown not long ago, reaction is in 
 all cases contrary in direction and equal in vigour to 
 action. The force E d, therefore, by the outlay of its 
 own vitality generates a force d e which acts in a par- 
 ticular manner to be more fully described presently. 
 B d remains wholly unaffected by the impact at d, since 
 the wall can, obviously, exercise no resistance to motion 
 which is parallel to its surface. The position of affairs, 
 therefore, is changed by the collision at d from the case 
 of a ball moved by c d, that is to say by b d and e d 
 jointly, into that of the same projectile impelled simul- 
 taneously by b d and d e. Continue b d in the same 
 straight line to A, making d a equal in length to d b, and 
 complete the parallelogram dafe. The resultant of 
 D A and d e will be the diagonal D f, and the ball will 
 be landed by d f at f. dp makes an angle with d e 
 which is equal to that made with it by c d, or, in other 
 words, the degree of obliquity of the rebound depends 
 on and precisely corresponds with that of the incidence. 
 
 The ricochet of a cannon ball, described by a techni- 
 cal term which has been appropriated by the language of 
 artillery to designate the bound of a projectile of a par- 
 ticular kind when it has been purposely dispatched in 
 such a manner as to skim the ground after the fashion of 
 the missile in the game of ducks and drakes, takes place 
 of course in strict conformity with the mechanical law 
 which has been stated. The same rule governs the 
 rebound, or, as it is called in this particular case, the 
 " reflection *>' of light from a smooth and bright surface. 
 The rule which defines the conditions under which re- 
 bound takes place being most noticeable, and having for 
 many reasons attracted the most attention in the case of 
 
218 
 
 children's toys. 
 
 light, lias been formulated in terms which refer to that 
 particular instance of its operation, although, as has 
 been seen, it is more widely applicable; it is thus known 
 as the law that the angles of incidence and reflection are 
 equal to one another. It is proper enough that the case 
 of light should be selected as the typical one to which the 
 terms of the law should point, for in that instance the 
 statement as to the equality of the angles of incidence 
 and reflection holds good in a precise sense. In the case 
 of rebound the result is only more or less approxi- 
 mately in conformity with the formula, since, as has 
 been said, there is no body which is perfectly elastic. 
 
 To return to the circumstances under which the re- 
 bound of a ball takes place, and which require some fur- 
 ther examination. The ball whose behaviour was under 
 consideration just now was supposed, for the purpose 
 of making the conditions of the problem as simple as 
 possible, to be perfectly elastic. From what was said 
 a short time back it will be understood that elasticity, 
 as tending to produce rebound, is the quality of struc- 
 ture or constitution in virtue of which the moving body, 
 while freely allowing some momentary alteration of its 
 form to take place under pressure, that is to say under 
 the force exerted upon it by reaction at the point of 
 collision with some fixed obstacle, immediately re- 
 assumes its former shape, as, and when, permitted to 
 do so by the diminution or cessation of that pressure, 
 that is to say as soon as the original momentum, being 
 spent, ceases to excite what is tantamount to action on 
 the part of the resisting surface. 
 
 Now no material, as was stated just now, is per- 
 fectly elastic. The india rubber of which the most 
 
children's toys. 
 
 219 
 
 elastic balls are made opposes some antagonism to the 
 temporary disarrangement of its component particles 
 under the blow which reaction, as has been explained, 
 virtually inflicts, and it does not readjust the con- 
 tour of its original figure with a degree of energy 
 quite equal to that of the force by which its original 
 shape was altered. A certain part, therefore, both 
 of the force of action, and of that of reaction, will 
 have spent itself through some channel other than that 
 which conduces to the production of a rebound ; this 
 ineffective portion will, as some of you no doubt know, 
 have taken the form of heat. This is a point on 
 which we can only bestow a passing allusion, since 
 the time at our disposal, like the india rubber of 
 which we have been speaking, is not infinitely elastic, 
 and cannot, therefore, be so stretched as to include 
 everything svithin its compass. It was necessary, how- 
 ever, to guard against the imputation or suggestion 
 of inaccuracy by mentioning that the conclusions to 
 which the working of ouivproblem led us as to the event- 
 ual position of the ball when the force of rebound has 
 been finally spent, will not be sustained by actual ex- 
 perience as being found to be in practice entirely true. 
 For predicating what this position would be in the case 
 of any given ball thrown against a fixed object at some 
 particular angle, and with a stated amount of force, 
 it is necessary that the precise degree of its elasticity 
 should, as one of the first essential conditions on which 
 the result must depend, be ascertained, and taken into 
 account, and that certain other data should be furn- 
 ished and their effect computed. 
 
 What has been said as to the series of occurrences 
 
220 
 
 CHILDBEDS TOYS. 
 
 which results in producing the bound of a ball is the 
 source of a familiar phenomenon of quite another kind 
 to which it will be worth our while to refer, since it 
 will illustrate the course of events which has been de- 
 scribed, and help to clench your recollection's hold 
 upon them. Suppose, then, that a bullet is tossed 
 gently through a window pane. The destruction which 
 it causes in its passage is great, and widely spread. 
 All round the hole which it makes, and for some dis- 
 tance in every direction, the glass is cracked and starred. 
 The degree of mischief which is altogether done is 
 found to be pretty nearly in inverse proportion to the 
 rapidity with which the bullet moved, that is to say, 
 the smaller the speed the greater the destruction. This 
 result is so noticeable and clear that it can never have 
 failed to attract attention, and in the old days of naval 
 warfare it was procured by express design, in the man- 
 ner which shall be explained. 
 
 In those times the general character of a battle at 
 sea was mainly that of the engagement, in pairs, of a 
 multiplicity of ships, each battering exclusively its one 
 private and particular antagonist, like the warriors 
 before Troy, who, according to Homer, seem to have 
 conducted their hostilities almost entirely by means of 
 duels. The leading principle of naval tactics was that 
 each ship was to lay itself alongside of the first enemy 
 who presented himself, for the purpose of a mutual 
 pounding at close quarters. The couple, frequently 
 lashed together for the more systematic conduct of the 
 business in hand, poured broadsides, as fast as they 
 could be fired, into one another's ribs, till one of the 
 two halls was pretty well smashed up into lucifer 
 
children's toys. 
 
 221 
 
 matches. In fighting under such conditions as these, 
 it was advantageous, and usual, to employ much smaller 
 charges of powder than were required at long ranges, 
 for the lower the velocity of the ball, provided only that 
 it had just sufficient energy to penetrate a ship's skin, 
 the more destructive was its effect in the way of pro- 
 ducing wide- spread rents and splinters. The reason of 
 this was as follows. 
 
 When collision takes place between two bodies one 
 of which is stationary and the other in rapid motion, 
 such particles of the former as happen to be situated 
 at the point of impact receive, of course, a blow whose 
 tendency is to push them backwards from the situation 
 which they occupy, and, through them, to drive the 
 mass which is behind them into retreat. If the blow 
 is sufficient to overcome the natural inertia of the body 
 which is at rest, and if this latter be at the same time 
 free to stir, movement is gradually imparted to it. 
 But it takes a certain time, however short, to induce 
 change of place in the whole mass which is thus im- 
 pelled. This statement must be taken upon trust as 
 true, if the reason for it does not happen to be at once 
 obvious to you, since to explain the point fully would 
 require a longer episode than can be afforded to it at 
 this moment. Now if this modicum of time, which, 
 however infinitesimal it may be, is none the less of 
 essential necessity for the purpose which has been 
 mentioned, be not allowed, the particles which first 
 encounter the blow have, as it were, to bear its whole 
 brunt and effect in their own persons. Thus, suppose 
 that a bullet be discharged from a pistol against a pane 
 of glass. The blow is in the highest degree smart and 
 
222 
 
 childeen's toys. 
 
 sudden. The small circular field of glass which is equal 
 in extent to the sectional area of the bullet, and which 
 is therefore subject to its direct attack, is driven before 
 it too peremptorily and hurriedly to allow it time to 
 impart any of its movement to the particles which are 
 in its immediate vicinity. It is thus carried before the 
 bullet, leaving a hole behind it which is almost as clear 
 and clean-cut as though it had been punched. If, on 
 the other hand, the stroke from the bullet be but a lan- 
 guid one, time is allowed for the accomplishment of a 
 drag and jar on the surrounding tract of glass, which 
 is thus torn and shattered. 
 
 The time-honoured feat of firing a tallow candle 
 through the panel of a deal door ceases to be marvellous 
 when the reason why an uglier wound, as was ex- 
 pounded just now, is inflicted by a comparatively 
 hesitating shot than by one of greater decision of 
 character, has been apprehended. The two phenomena 
 are, obviously enough, all of a piece with one another. 
 The fact to which the celebrated Engineer, Sir I. 
 Brunei, called attention, that the mode of breakage 
 of a bar of iron displays the nature of the force and 
 the degree of time used in the operation, is explicable 
 by the same reasoning as has been applied to the frac- 
 ture of glass. If a bar of iron be gradually reft in sun- 
 der, or, so to express it, slowly worked apart by a series 
 of dull thumps, the structure which is laid bare at the 
 place of rupture is fibrous, which means more or less 
 drawn out into threads. If, on the other hand, it is 
 struck into two pieces by a single brisk and decisive 
 bang, the exposed surfaces of the wound disclose a crys- 
 talline character, that is to say, a fracture of a sharp and 
 
children's toys. 
 
 223 
 
 gritty kind, indicating that the continuous arrangement 
 of the particles constituting the bar was destroyed at 
 the point where the blow fell so instantaneously that 
 the whole effect of the stroke made itself felt, and ended, 
 before any lateral disturbance could extend into the 
 adjacent parts. The relation which phenomena such as 
 have been described as consequent on impact bear to 
 those which occasion and attend rebound needs no 
 comment. 
 
 The spectacle of a bounding ball following with 
 exact and implicit obedience, at each and every point of 
 its career, the joint dictates of the forces to which its 
 motions are due tends to induce a more real and vivid 
 appreciation of the fact that the nonentity which goes 
 by the name of Chance has no share whatever in the 
 proceedings. It also invigorates the perception of the 
 truth that anything which is cast at random into the air, 
 although it may present some delusive appearance of 
 enjoying more absolute liberty than is possessed by 
 objects which are under the immediate dominion of 
 powers by which they are visibly controlled, is never 
 surrendered for a single instant, or to the extent of a 
 hair's breadth, to the caprices of accident. 
 
 A stone, for example, when flung by a school-boy, 
 does not manifestly pursue a course which is prescribed 
 to it by clear and fixed conditions, yet throughout the 
 whole of its journey, including its eventual fall to the 
 ground, it is as despotically governed and directed by 
 a set of known forces as it was by the hand of the thrower 
 before it quitted his grasp. Given the conditions under 
 which it is projected, its trajectory, that is to say its 
 entire line of flight from its start to its finish, can be 
 
224 
 
 children's toys. 
 
 accurately foretold. The character of the track which 
 is pursued, unless the stone has been thrown quite 
 straight upwards, is of a very interesting kind, as will 
 appear presently. There will be three forces acting 
 upon it, during the whole time that it continues to pos- 
 sess any motion. One of these will be, at the first start, 
 the impulse then imparted to it, and afterwards, the 
 continually dwindling residue, for the time being, of 
 that impetus. The second will be the force of gravity 
 pulling it towards the earth ; and the third will be the 
 resistance of the air opposing its progress whatever 
 may be the direction of motion. Sooner or later either 
 gravity, or the resistance of the air, would inevitably, 
 of itself alone, prevail against and destroy impetus, 
 however strong, because this last is a finite force whose 
 whole energy is put forth at the first onset, and is never 
 af terwards recruited. The attraction of gravity, on the 
 other hand, is an inexhaustible power, and the resist- 
 ance of the air is actually generated by the passage of 
 the missile as it elbows its way, so to speak, through 
 the throng of particles which make up the atmosphere. 
 This resistance never ceases to oppose impetus, and thus 
 gradually tires it down by an antagonism which is 
 pertinaciously maintained so long as there is even the 
 smallest and feeblest remnant of motion left for it to 
 exterminate. 
 
 If the stone be thrown straight upwards in a 
 perpendicular line, it must plainly enough return by 
 the same way that it went as soon as the momentum 
 with which it was originally gifted has been subdued 
 by the adversaries which have been mentioned. If it 
 be flung in any other direction whatever than a verti- 
 
children's tots. 
 
 225 
 
 cal one, its path will be in some variety or other of 
 the particular species of curve which is termed a para- 
 bola. We cannot go into the mathematics or even any 
 precise description of a parabola here, but if you wish to 
 see a figure of the kind in question, a model may con- 
 vey a sort of notion of what the curve in question is in 
 its general personal appearance, although giving no 
 idea of its peculiar characteristics. 
 
 A parabola is a section of a cone ; that is to say, if 
 a cone such as will be described in a moment were to 
 be sliced through by a cut made within certain limits, 
 the exterior boundary of the surface which, as is to be 
 conceived, would be laid bare by the passage of the 
 knife would be, in form, a parabola. A cone is a figure 
 somewhat resembling a pyramid in its general aspect. 
 Its top or apex is a sharp point. Properly speaking, 
 it has no bottom, or base, at all. For it is supposed 
 to be generated by two straight lines of indefinite 
 length which meet, like the legs of a pair of compasses, 
 and are then twisted round an axis common to both 
 as if they were the arms of the governor in a steam- 
 engine. 
 
 No complete presentment, of course, of the in- 
 definitely large figure which would be thus traced can 
 
 Q 
 
223 
 
 children's toys. 
 
 be given by any model or diagram, or even indeed, 
 except very imperfectly, by tlie imagination, which can 
 only cope with such magnitudes, of whatever kind they 
 may be, as are comprised within small and strict limits, 
 but the model of a certain finite portion, adjacent to 
 the apex, of a cone will serve for our present purposes. 
 It will be observed that a sugar-loaf does not come 
 under the definition of a cone which has just been 
 given, since it has a shoulder, or bulging portion all 
 round, near its tip; while in a mathematical cone a 
 line drawn from any point on the exterior surface of 
 the figure to the apex is straight. Pastilles, military 
 tents, extinguishers, and the cut ends of pencils are 
 true cones. 
 
 Now suppose a section of the wooden cone which is 
 before you to be made by slicing it aslant in any direc- 
 tion, provided only that the cut is made in such a 
 manner as to enter a side of the figure, aud go through 
 its base. A model like this, which is readily to be ob- 
 tained at almost any optician's for a shilling or so, is 
 for convenience already divided into such sections as 
 are required, so that it has only to be taken apart to 
 display them. The outside edge of the wound which 
 results from any cut thus executed is a curve of two 
 parts or limbs, and somewhat resembles as a whole one 
 of the terminal portions of an oval. Such a curve is 
 called a parabola. Many comets move in parabolas. 
 If the cone were to be sliced in another and more 
 horizontal direction so as not to traverse the base, the 
 edge of the cut would be what is called an ellipse, 
 which represents the path of the Earth and of other 
 
children's toys. 
 
 227 
 
 planets. Carved after a third fashion, more perpen- 
 dicularly, the divided parts of the cone would present 
 what is call an hyperbola, a curve which some comets, 
 perhaps, describe in their movements. 
 
 It thus appears that unless some idea of the nature 
 and properties of the curves which are presented by the 
 sections of a cone be acquired, the motions of a ball 
 cannot be understood. The study of the law which 
 governs the conduct of every ball and every stone which 
 is thrown into the air is hence seen to be a necessary 
 preliminary to the acquisition of the first rudiments of 
 elementary astronomy. 
 
 Exception might of course be taken to the foregoing 
 rough account of a cone on the ground that the figure 
 in question is not quite so simple as the description 
 which has been given of it would suggest. It might 
 be objected that the idea of a cone which has been 
 conveyed is that of a single figure with a circular base 
 and pointed apex, like the spire of a church, while, as 
 it might be said, a complete cone is double, like an 
 hour-glass. This, no doubt, is so, but as we have been 
 concerned with the parabola only, a curve which has to 
 do with the section of a cone made wholly on one side 
 of the apex, it was not thought worth while to en- 
 cumber the text with details which were practically 
 unnecessary. 
 
 It may be mentioned that anyone who desires to 
 see a parabola in the flesh, if that expression may be 
 used to signify its visible personality, may generate the 
 figure in question by putting on a flat table a lamp 
 whose flame is just on a level with the top of an upright 
 
228 
 
 childken's toys. 
 
 hoop placed alongside of it. The shadow whose head 
 will be found to touch the point on which the hoop 
 stands will be a parabola. 
 
 The reason why a ball rolls when despatched along 
 a surface claims examination, but it will be more con- 
 venient that this matter should be looked into presently 
 when we come to consider the motions of a hoop. 
 
CHAPTER IX. 
 
 ^]HE Kaleidoscope, to which we will now turn, 
 is one of the youngest of toys. It was in- 
 vented by Sir David Brewster about 50 years 
 ago. The principle, however, on which it 
 is founded was not new, since it must have been 
 then, as it is at this day, exemplified in almost every 
 drawing-room, that is to say in every room which 
 happens to have two mirrors opposite to one another 
 on different walls. It cannot fail to be noticed that 
 whenever this arrangement exists any object interven- 
 ing between the two glasses so as to be reflected in 
 them, is repeated an indefinite number of times in both. 
 To take, as an example, a prominent and noticeable 
 object by which the effect in question is most strikingly 
 presented, namely, a chandelier with lighted candles. 
 This, when hanging in the intermediate space between 
 the mirrors, will produce in each of them a long vista 
 of illumination, extending seemingly throughout an in- 
 terminable chamber, like the Burlington Arcade con- 
 tinued out into infinite space, to which the room will 
 to all appearance have stretched itself. 
 
 The multiplication of the lights in the manner which 
 
230 
 
 children's toys. 
 
 is thus witnessed takes place in the usual and necessary 
 course of reflection by common mirrors. For when 
 you look at yourself in a looking-glass you see a 
 " counterfeit presentment of your own face, together 
 with as much more of your personality as the area of 
 the glass is large enough to display. If you approach 
 the glass more nearly, your " double " approaches 
 also, and if you recede from it your other self does 
 likewise. Your image, therefore, to all visual intents 
 and purposes, is your own self, placed at exactly the 
 same distance behind the glass as you in fact stand 
 before it. 
 
 If a second mirror be now set parallel to the first, 
 but behind you, it will be bound to show, first of all, 
 the direct reflection of your person, and you will 
 appear to be as much removed to the back of the 
 glass as you are, in truth, from its front. But to the 
 perceptions of this second mirror your image reflected 
 in the first mirror is for all practical purposes another 
 real and bodily version of you, only a little farther off, 
 inasmuch as the surface of the first mirror is more 
 remote from the surface of the second mirror than you 
 are. This image, therefore, takes its place in the 
 second mirror at some point or other behind the one 
 which is already there. This second image in its turn 
 becomes virtually, as far as the first mirror is concerned, 
 an original, and is accepted and represented by it as 
 such, taking, when this occurs, a position which may 
 readily be determined by anyone who, like the glass, 
 exercises a little reflection. 
 
 We thus get by repeated reflections an indefinite 
 number of images in each mirror. The series would, of 
 
children's toys. 
 
 231 
 
 course, be absolutely infinite were it not that reflection, 
 like everything else in this world, is more or less im- 
 perfect, so that on each occasion when it takes place a 
 certain amount of light is lost. Hence each succeeding 
 image is fainter than its predecessor, till at last the 
 series fades away through increasingly dim stages into 
 nothingness. Standing between the mirrors you would 
 not be able to behold yourself thus multiplied, since 
 the foremost image in each glass would interrupt the 
 view from your position of the figures behind it, but 
 any one looking downwards from the ceiling would see 
 the effects described. 
 
 A double series of images such as has been men- 
 tioned may be called into being by the easy expedient 
 of holding or fixing two looking-glasses vertically on 
 their edges parallel to and facing one another. Place 
 any object which may be at hand, a bright one for 
 choice, between them, and it will be immediately 
 reproduced, as has been predicted, in two long trains 
 of semblances of itself extending on either side into 
 dim vacuity. Now bring either the upper or the 
 farther edges of the mirrors nearer to one another, 
 and observe the result. The two lines of images curl, 
 as will be noticed, in the former case upwards, and in 
 the latter horizontally, till at length they unite and 
 form a complete ring. This circle will be found to be 
 one whose centre is at the point where the mirrors meet, 
 and whose radius is the distance from that centre of 
 the object which generates the images. Why it is 
 that a circular series of images is obtained by the 
 arrangement described ought not, after what has been 
 said, to be a riddle difficult of solution. 
 
232 
 
 children's toys. 
 
 Now suppose that it is wished to keep the mirrors 
 fixed in some given position with reference to one 
 another, say with their upper edges in contact, and 
 with their reflecting surfaces inclined to one another 
 at a particular angle which has been found to conduce 
 to the best optical effects, and which is therefore 
 desirable to preserve. The most convenient mode of 
 giving assured permanency to any successful arrange- 
 ment of the mirrors which may have been lighted on 
 will be by surrounding them with a stiff tube, and 
 fastening them into it in their existing positions. In- 
 stead of continually changing the object for the pur- 
 pose of giving variety to the spectacles which the 
 mirrors are to display, it will be less troublesome to 
 close in the end of the tube which is to be farthest 
 from the eye with two discs of glass parallel to one 
 another and just far enough apart to form a shallow 
 box in which may be placed some small loose bits of 
 any coloured material which will of their own accord 
 tumble at haphazard into different modes of arrange- 
 ment as the cylinder is turned round. The glass 
 which forms the inner side of the box should of 
 course be clear. That on the outside should be of 
 ground glass, so as to be translucent, but not trans- 
 parent. It will thus admit light to the tube, while 
 preventing any view of external objects from mingling 
 with that of the coloured scraps. Finally, let the end 
 of the tube which is nearest the eye be shut in with 
 any opaque substance having a hole in the middle 
 sufficiently large to be conveniently looked through. 
 A kaleidoscope has now been manufactured. Of course, 
 for practical convenience, it will be expedient to use 
 
children's toys. 
 
 233 
 
 long strips of silvered glass, instead of looking-glasses, 
 as mirrors. 
 
 On looking through the eye-hole, the coloured 
 scraps are seen arranged apparently in a circle, so that 
 they form an orderly pattern which successfully per- 
 sonates design. No one can have failed to remark 
 the optical effect of reflection in still water. The real 
 object or scene which is mirrored, however irregular 
 and ragged in outline it maybe, acquires, when conjoined 
 with its reversed image, which it meets at the sur- 
 face of the pool, the character of a symmetrical and 
 well-balanced picture, inasmuch as similar figures are 
 disposed in an order which, although reversed, is still 
 one of exact correspondence, on either side of a par- 
 ticular dividing line. In the kaleidoscope, the outline 
 at any given moment of the little pile of coloured 
 scraps, and the internal arrangement of its component 
 items which at the same time prevails, represent the 
 state of things brought about by the last preceding 
 revolution of the cylinder, and as far as the person 
 who is using the instrument is concerned, are entirely 
 unforeseen and accidental. It is altogether owing to 
 the reduplication of the composite pictures which are 
 generated by the union through reflection of image 
 with reality that a continuous and complete pattern 
 is due. 
 
 Whoever desires to understand a kaleidoscope 
 should make one, since this may be done at an insigni- 
 ficant cost both of time and money. Various points 
 which cannot be dwelt upon here will then present 
 themselves to notice, one of which will be the follow- 
 ing. The angle at which the mirrors are inclined to 
 
234 
 
 children's toys. 
 
 one another must be some aliquot part of 360 degrees, 
 and the number of the images formed will depend on 
 the size of this angle. The larger the angle, the 
 smaller will be the number of images. If, when the 
 kaleidoscope is in action, a pattern happens to be pre- 
 sented which is exceptionally beautiful, and therefore 
 worth preserving by means of a copy, the instrument 
 must be kept perfectly still until the design has been 
 transferred to paper. For the variety of mosaic designs 
 which even a couple of dozen, or a less number, of frag- 
 ments of coloured glass suffice to form by the different 
 modes of combination of which they are susceptible is, 
 practically speaking, infinite. It is therefore no romance, 
 but a mere dry and simple mathematical truth, which 
 any one possessing an acquaintance with elementary 
 arithmetic can readily verify, to say that a kaleidoscope 
 containing no more than, say, 20 of such bits in its 
 terminal chamber might be kept continually turning 
 for ages, before, according to a strict estimate of pro- 
 babilities, any pattern which had once come upon the 
 scene would be likely to recur. 
 
 The observation which is applicable to almost every 
 toy, that it will admit of expansion and improvement 
 till it becomes a source of a variety of instructive and 
 interesting' effects, is especially true of the kaleido- 
 scope. By a suitable modification of the tube the glass 
 box may be dispensed with, and instead of the coloured 
 fragments, which, with all their capability for entering 
 into fresh combinations produce nevertheless a certain 
 sameness of general effect, external objects may be 
 brought into the field of view. If these be in motion, 
 such as trees blown by the wind, or carriages, or waves 
 
children's toys. 
 
 235 
 
 of the sea, an endless variety of self- sliif ting, curious, 
 and amusing designs will be presented to the eye. 
 More brilliant effects, also, than those which are wit- 
 nessed in ordinary kaleidoscopes are procurable by 
 substituting for the mirrors a prism of clear and un- 
 silvered glass. This will be so for a reason which must 
 be given at some length. 
 
 It was mentioned just now that on every occasion 
 when light is reflected there is some loss on the trans- 
 action. A certain percentage of the rays which fall 
 on any surface are dissipated irregularly, (" scattered/' 
 as it is called,) or else absorbed. The waste which 
 always occurs in this manner is greater or less in pro- 
 portion to the degree of reflecting power which the 
 surface in question happens to possess. Even in the 
 case of reflecting telescopes, where the speculum or 
 mirror is the very best thing of the kind which human 
 labour and skill can produce, and where expense of 
 construction is, in the too familiar, though vulgar and 
 confused, phrase of the Servants' Hall, " no object," 
 nearly 50 per cent, of the light which falls upon the 
 reflector is lost. If a mirror did its work completely, 
 that is to say, if it honestly repaid all that it receives 
 in the way of light up to the uttermost beam, it would 
 be itself invisible. It would present to the eye nothing 
 but an absolutely perfect counterfeit presentment of 
 nature in an extremely vivid picture of the objects 
 whose images falling upon its surface were reflected 
 thence to the eye of the spectator. A looking-glass, 
 though for ordinary purposes the most convenient form 
 of mirror, is not only a reckless spendthrift of light, 
 but does its business of reflection in a confused and 
 
236 
 
 children's toys. 
 
 imperfect manner, which, if our perceptions were more 
 keen and delicate than they are, would be uncomfort- 
 ably manifest and annoying. You will discern why 
 this is so if you bear in mind that a main part of the 
 work of reflecting is done by the amalgam of quick- 
 silver and tin with which the back of the mirror is 
 coated. 
 
 It may be observed here by way of parenthesis that 
 the idea of the employment of polished metal as a re- 
 flector may seem to have some sort of impression of 
 novelty about it, but next in time to clear pools, such 
 as Eve must have done her hair by, and which were the 
 first looking-glasses, came metal reflectors. Those made 
 by the ancients were, of course, functionaries of a far 
 simpler and less efficient order than the brilliant im- 
 plements composed, usually, of copper and tin, with, 
 sometimes, the addition of other metallic ingredients, 
 which modern astronomers have enlisted in their serv- 
 ice. Glass mirrors are, in point of date, mere institu- 
 tions of yesterday as compared with metal ones. Now 
 a plate of polished metal, even if it be in itself abso- 
 lutely perfect as a mirror, will be seriously impaired in 
 efficiency if a screen of not altogether complete trans- 
 parency be interposed between it and the objects which 
 it is set to reflect. If, for example, it be plunged into 
 clear water, some of the rays which would otherwise 
 have fallen upon it will be reflected by the fluid, and 
 will mingle confusedly with those which are on their 
 way to and from it. Besides which, the light which is 
 not summarily turned back by the water will, both in 
 coming and going, be attenuated in quantity, and di- 
 verted from its proper track, by absorption and refrac- 
 
children's toys. 
 
 237 
 
 tion. The behaviour of a glass mirror is prejudicially- 
 affected by circumstances which, are of a nature exactly 
 similar to those which have been just supposed. 
 
 It is, no doubt, true that in spite of the defects which 
 have been adverted to glass specula are used, and are 
 perhaps even to be preferred, on the whole, to metal 
 ones for telescopes, but this is for special reasons which 
 are as follows. The face of such a mirror, of whatever 
 substance it may be composed, must, as need scarcely 
 be said, be kept scrupulously bright and clean. A 
 speculum, like a lady's reputation, leaves everything to 
 be desired unless it be absolutely spotless. But it is 
 found that the brilliancy of a metal one cannot be pre- 
 served for more than two years without scouring. In 
 cold weather, too, there is constant condensation and 
 freezing upon it of the moisture of the air, rendering it 
 too dim for use unless it be frequently wiped. It is, 
 however, hardly possible to rub a mirror which is wholly 
 composed of metal without putting it a little out of its 
 true shape, or generating undulations or depressions in 
 its surface, thus vitiating the accuracy, and, as a con- 
 sequence, largely reducing the value of the images 
 which it presents. To this inconvenience is to be 
 added that a metal speculum must be immensely mas- 
 sive, for otherwise it is likely to bend of itself, in which 
 case it would give distorted images. Metal of the 
 kind required is also most difficult to work, being so 
 brittle that it constantly breaks without the least pro- 
 vocation. 
 
 Glass does not suffer disarrangement of contour 
 to anything like a similar degree under polishing ; 
 it has also more stiffness of natural constitution, and 
 
238 
 
 childeen's toys. 
 
 is easy to manufacture. It has moreover the great 
 virtue of maintaining what may be called an imper- 
 turbable smoothness of countenance, and is therefore 
 serviceable as a facing. Its vocation is, of course, 
 merely that of acting as a framework to support the 
 true and sole reflecting surface, which is the polished 
 silver at the back. All things considered, perhaps the 
 best form of speculum is that of a fabric of glass coated 
 in front with a very thin layer of polished silver. 
 
 Now glass, as everybody knows, will, under certain 
 conditions, act as a mirror without being backed by 
 amalgam, The ghost at the Polytechnic, for example, 
 did not, like other ghosts, owe his existence simply to 
 the credulity which belongs to want of education, but to 
 a contrivance of which a sheet of clear glass, adjusted 
 to a particular angle with reference to the spectators, 
 
 was a main feature. Two reflectors of plain glass 
 without any metal backing, one of them a flat disc, and 
 the other a rectangular prism, form part of the ac- 
 coutrements of every good microscope. In a pretty 
 
children's tots. 
 
 239 
 
 drawing-room ornament which has lately become com- 
 mon, a figure is painted on one of the facets only of a 
 glass prism, but to a spectator viewing the thing from 
 a particular angle of view the picture is seen in dupli- 
 cate, reflection supplying a second image which is 
 indistinguishable from the first one. 
 
 A prism which is to be employed as a reflector must 
 be shaped as follows. One of its corners must be a 
 right angle, or must be one of not less than about 83 
 degrees, and the sides inclosing this must be equal to 
 one another in length. Light allowed to enter such a 
 prism as this through one of its two equal sides, and 
 to fall upon the third, which will be the longest of the 
 three, will be dispatched by reflection from this last 
 outwards through the remaining member of the trio. 
 The contrivance for copying drawings which must be 
 familiar to you as a popular toy, is founded on this 
 faculty for reflection which plain glass, when suitably 
 adjusted, possesses. The drawing which is to be copied, 
 and the sheet on which it is to be reproduced, are laid 
 flat on their backs alongside of one another, and a plate 
 of glass is fixed vertically between them. It will be 
 seen at a glance how, by taking advantage of the light- 
 transmitting and reflecting faculties of glass at the same 
 time the making of the required copy becomes a mere 
 process of tracing. 
 
 An account of the effect which is witnessed in all 
 these cases may be very roughly and generally given as 
 follows. Light falling with no more than a certain 
 degree of obliquity on a flat piece of glass, passes 
 through it and emerges at the other side, bent out of 
 its original course in a manner which is called refraction. 
 
240 
 
 children's toys. 
 
 But if the slant with which it falls upon the glass 
 have more than a given inclination, or, as it is ex- 
 pressed, if the line of incidence make a greater angle 
 than one which is called the " critical/' or " limiting 33 
 angle with a perpendicular drawn to the surface which 
 is met, then reflection instead of refraction takes place. 
 This limiting angle varies with the greater or less re- 
 fractive power of the medium through which the light 
 passes. 
 
 A tumbler of water with a spoon in it will ex- 
 hibit the phenomenon of reflection substituting itself 
 for refraction under such conditions as have been men- 
 tioned. For when the tumbler is held high enough to 
 enable a spectator to look up to the surface of the 
 water from below, the spoon will be seen reflected by 
 the interior face of the flat ceiling of the liquid in that 
 direction. The vividness of the mirrored image will 
 be striking, and this circumstance will of itself suggest 
 what is in fact true as a general rule, namely, that re- 
 flection takes place with the most economy of light, 
 and therefore in the most efficient manner, when it 
 occurs within the medium through which the rays pass. 
 Hence it becomes apparent why a glass prism might be 
 advantageously substituted for the mirrors in a kaleido- 
 scope, since the brilliancy of the optical effects would 
 be thereby much enhanced. Prisms, therefore^ would 
 no doubt be used if expense could be disregarded, but 
 the ordinary mirrors are preferred for their cheapness. 
 
CHAPTER X. 
 
 OPS are the most interesting of all toys. It 
 would be a pleasant occupation for anyone 
 who had the time to spare, to trace their 
 history. As a proof of their antiquity it 
 may be mentioned that they were popular with the 
 Romans as many, at all events, as 18 or 19 centuries 
 ago, and probably much earlier still. Virgil, who 
 wrote most of his poems about the time of the 
 birth of Christ, describes a party of youths entertain- 
 ing themselves by keeping a whipping-top spinning. 
 The passage in the iEneid in which the scene is de- 
 picted is familiar enough to every schoolboy. Tops 
 are also referred to by Juvenal, and by Persius, who 
 both speak of them as if they were old and favourite 
 institutions. The Japanese, whose civilization, though 
 not of the same pattern as ours, is very ancient, are 
 great lovers of tops, and make them spin and go 
 through all sorts of performances with a docility, pre- 
 cision, and even a seeming intelligence, which the less 
 adroit and delicate touch of the finger-tips grown in 
 this quarter of the globe quite fails to impart. A top, 
 therefore, is one thing to a Japanese, and another to 
 
 R 
 
242 
 
 children's toys. 
 
 an Englishman : similarly, to an ignorant person it is 
 but a toy, while to an educated mind it is no mere 
 plaything only, but an instrument by which the work- 
 ing of some of the most important laws in Astronomy 
 and physical science is strikingly illustrated. The 
 present Astronomer Royal has somewhere or other 
 pointed out the claims which a top thus possesses to 
 attention. Mr. Herbert Spencer, also, in his " First 
 Principles," dwells upon the various phenomena ex- 
 hibited in the spinning of a top as aiding to elucidate 
 particular points in the general order of creation. 
 
 Thus much having been premised for the purpose 
 of bespeaking your careful and serious attention, let us 
 spin a top, and see what occurrences ensue which are 
 noteworthy. Regarding the space of time during 
 which it spins as its period of vitality, or, in other 
 words, as being, for the top, a lifetime, what may be 
 called its early youth, when it first assumes the cha- 
 racter of an animated being, is one of vehement and 
 tempestuous action. Under the gentle and persuasive, 
 but efficient, impulse which a Japanese manipulator 
 imparts, this is not so, since a top, if set going by a 
 competent artist, never bounces about, but devotes 
 its whole energies to its proper business of spinning. 
 But when it is started by a maladroit operator, it gen- 
 erally begins by hopping and dashing excitedly over 
 the surface on which it is set going, and bumping itself 
 against any sides inclosing that arena which it can 
 manage to reach, like a lively bluebottle fly caught 
 under a tumbler. Having sowed its wild oats by thus 
 extravagantly squandering much of its endowment of 
 vital energy, it waltzes round and round with a reeling 
 
CHILDBEDS TOYS. 
 
 243 
 
 motion, which is gradually toned down into a demeanour 
 of more and more composure, till at last it becomes 
 stationary and upright, and spins tranquilly for some 
 while in that position. Eventually, a tremulous motion 
 discloses itself, which, becoming aggravated, develops 
 into a wabble of a more and more pronounced kind, 
 till at last, in one of the lurches which supervene, the 
 body of the top scrapes against the floor. Spasms of 
 vehement action now set in, during which the top bangs 
 about on its side. These are soon exhausted, and at 
 their close the top lies still and dead. What have been 
 the several motives of the successive phases of conduct 
 which have been described, and with which we are so 
 familiar ? 
 
 To begin with the first. The top is set spin- 
 ning by imparting to its axle a brisk movement of 
 revolution by means of the uncoiling of a string wound 
 upon it for this purpose. The person who spins the 
 top giving a necessarily hard pull at the string with his 
 right hand, must resist this tug by means of the handle 
 which he holds in his left, for otherwise the top, of 
 course, would be drawn away bodily from the locality 
 where it is to be set going. Ultimately, when the in- 
 side end of the coil of string leaves the axle, the pull 
 exerted by the right hand suddenly ceases. If the 
 counteracting force applied through the handle be not 
 relaxed and discontinued in precise correspondence with 
 the diminution and cessation of its opponent's effort, 
 which is a very difficult thing to adjust, the top, at the 
 moment when it is released from the tutelage of its 
 controlling appliances, receives an unintended impulse 
 which contributes nothing to its spinning, and which 
 
244 
 
 children's toys. 
 
 carries it bodily in some lateral direction across the 
 surface of the arena where its performance is to take 
 place. This movement of translation is opposed by two 
 forces, one of which, the resistance of the air, is in this 
 case so trifling that it is not worth consideration. The 
 other, which is that which really, and very soon, arrests 
 the movement in question is the friction of the point 
 of the peg on which the top spins against the surface 
 over which it travels. Friction being persistent and 
 inexhaustible, and the force to which the travelling 
 just spoken of is due being of only finite quantity, the 
 destruction of the latter by the former agency is neces- 
 sarily a question of time only, and whenever this con- 
 summation is reached, the top comes to anchor at one 
 spot. 
 
 Here, it presents phenomena of movement of a 
 new kind, since it is observed to wave, as it were, its 
 axle in circles, thus, as upon consideration will be mani- 
 fest, describing in the air the surfaces of mathematical 
 cones. The apex of all such cones is, of course, at the 
 point upon which the top spins. These circles are at 
 first large, the inclination of the axle diverging by a 
 large angle from the perpendicular, so that its upper 
 end points to the walls, perhaps, of the room, or at any 
 rate to the exterior suburbs of the ceiling. The circles 
 gradually shrink, the axle describing, in real truth, a 
 spiral. The limit of convolution is ultimately reached 
 when the angle which the axle makes with the perpen- 
 dicular vanishes, and the top then spins with so smooth 
 and imperceptible a motion, a " motionless motion " as 
 one might call it, that it is said, in the popular phrase, 
 to be " asleep. " The French describe this condition 
 
children's toys. 
 
 245 
 
 of things in which the result of the action of dynamical 
 forces, that is to say, of forces producing motion, is 
 stillness, such as that of a sleeping top, by the expres- 
 sion " equilibrium mobile." 
 
 But " Why," it may be asked, " will not the axle 
 of the top rest satisfied with any other than a verti- 
 cal position ? That is to say, suppose the top were 
 to be started with its axle pointing at some one 
 particular corner of the room, why should not this 
 attitude be contentedly maintained ? " The reply is 
 that if the top were left to follow exclusively the 
 bent imparted to it by the forces with which it is 
 animated when it is first set spinning, it would con- 
 tinue in the pose which is just assumed, and not by 
 a mere passive acquiescence only, for that under the 
 influences dominating its movements it would resist 
 the disturbance of that attitude. This would be the 
 case under the general law which is found to hold good, 
 that the axis of any rotating body has a strong dis- 
 position to permanency. If a quoit is thrown, it is 
 purposely made to revolve as it flies by a twirl given to 
 it at the moment when it is dispatched upon its errand, 
 so that its behaviour is suggestive of a wheel running 
 one way but carried another. The spinning tends to 
 keep the quoit in one attitude throughout its whole 
 course, and thus to render its flight more true than it 
 would be if it wabbled. Saturn's ring (or rings, for it 
 is a double one), which preserves the same unchanging 
 attitude as it circles through space, illustrates on a grand 
 scale the characteristic faculty which a spinning quoit 
 presents of retaining the same pose throughout its 
 flight. The result is in each case due to the same cause. 
 
246 
 
 children's toys. 
 
 Just now, as you will remember, we had occasion 
 to inquire why it is that arrows, rifle-balls, and other 
 missiles, are made to spin. One advantage to be gained 
 by causing them to do so was then marked, and a 
 second has now come in view. For the spinning, as 
 tending to impart constancy of attitude to the axis, 
 promotes, of course, the result of keeping the projectile 
 in the way it should go. The effect of revolution on 
 an axis is illustrated by a child's hoop, which is kept 
 by this means from falling as long as it continues to be 
 possessed of some tolerable quantity of rolling motion. 
 It is also strikingly witnessed in the proceedings of the 
 gyroscope. In the gyroscope, when it is put in action, 
 the movement of revolution, as long as it is imbued 
 with a considerable degree of vigour, has so much 
 determination to keep its axis in its existing position 
 for the time being, whatever that may be, that it is 
 capable of maintaining a heavy brass ring, which is 
 otherwise unsupported, in a horizontal position, or in- 
 clined at some angle to the perpendicular. There is a 
 trite quotation, 
 
 " The very law that moulds a tear 
 And bids it trickle from its source, 
 That law preserves the Earth a sphere, 
 And guides the planets in their course." 
 
 The lines would apply to a multitude of other cases in 
 the sense of conveying the remark that King Law's 
 sceptre is wielded over a vast crowd of subjects, big 
 and small, but that all of them alike conform with loyal 
 and scrupulous exactitude to the ordinances established 
 within his dominions. 
 
 The permanence of an axis of rotation is an in- 
 
children's toys. 
 
 247 
 
 stance of a rule governing matters of extremely 
 varied dimensions, since the phenomenon in question, 
 while it is exemplified by the movements of a top, a 
 quoit, a shuttlecock, and a thousand other toys, is 
 illustrated by a working diagram on a larger scale, 
 but not a bit better, by the preservation of the atti- 
 tude of the line joining the North with the South 
 Pole as our globe rushes through space. The same 
 result of forces producing motion, or dynamical effect, 
 as it is called, which keeps a hoop erect *when rolling, 
 and thus endues it with the charm which it possesses 
 for Master Tommy, (since if it did not go tolerably 
 upright it could not be trundled,) gives, as another of 
 its effects, the four seasons, Spring, Summer, Autumn, 
 and Winter. If tops should cease to stand upright 
 when in full spin, great changes, revolutionizing the 
 general order of creation as now established, must 
 occur at the same time; for should the Earth's axis 
 lose its conservatism of posture, one of the consequences 
 which cannot but at once ensue will be this, that our 
 summers will be colder than our winters, since, as most 
 people know, we are farther from the Sun at midsum- 
 mer than we are at Christmas. All this will be 
 thoroughly understood before the end of the first half- 
 hour which is devoted to making acquaintance with 
 elementary Astronomy. 
 
 From what has been said, it is clear that a top, if 
 set to spin rapidly, and if its behaviour were not 
 affected by any influences other than those which have 
 been hitherto noticed, would retain, until its speed 
 flagged, the posture assumed at its first start. But it 
 does as a matter of fact raise itself to a vertical position 
 
248 
 
 children's toys. 
 
 in spite of the opposition of gravity , and of the forcible 
 inducements to maintain an unaltered trim which its 
 spinning, as has been seen, creates. An answer to the 
 riddle here presented for solution is to be looked for at 
 the tip of the peg on which the top spins. If there 
 were no friction at the point of contact of the tip with 
 the surface on which it rests, the top would not raise 
 itself to an erect position at all. But there never is, 
 and cannot be, either a point or a surface so consti- 
 tuted as that there will not be a grinding action be- 
 tween them where they meet, if either of them is in 
 motion and the other not so. Look at a fine needle 
 through a microscope of even but low power, and it is 
 seen to be a rough barge pole in miniature, and corre- 
 spondingly blunt. How it is that friction exerted by 
 the motion of the tip at the point in question has the 
 effect of causing the axis of the top to become erect is 
 a problem of some little intricacy, requiring a deliberate 
 as well as a close attention, which could not expediently 
 be bestowed upon it at this moment. The whereabouts 
 of the key to this question will be sufficiently indicated 
 to those who may desire to hunt it up by directing at- 
 tention to the fact, that whenever the top is not upright 
 it keeps rolling round, like a skater doing the outside 
 edge, upon a rim of its tip. 
 
 We have thus watched our top, after its initial 
 period of excitement and irregularity, becoming sta- 
 tionary on one spot, and then brandishing, as it were, 
 its axle in continually diminishing curves, which, if they 
 could make their mark upon paper, would be like those 
 of a Catherine wheel, till at last on reaching their centre, 
 or nucleus, no farther convolution remains possible; 
 
children's toys. 
 
 249 
 
 and we have seen the top then standing erect, with its 
 central line vertical, and actually divested of all move- 
 ment except one, which is imperceptible. The complete 
 stillness of the axle, whatever the speed of revolution 
 may be of the body which environs it, whether this be 
 a top, or anything else, reminds one of the picturesque 
 expression which Tennyson uses of " the whirlwind's 
 eye of calm," alluding to the circular sweep of cyclones, 
 eddying as they do, after the fashion which their name 
 indicates, round a nucleus of undisturbed tranquillity. 
 The analogy is strengthened by the circumstance that 
 the same Latin word " turbo " stands both for top, the 
 typical representative of a spinning object, and for 
 whirlwind. 
 
 The top having raised itself to the full height 
 which its stature permits, and poising itself on tiptoe, 
 " equilibrium mobile " is now established of such per- 
 fect quietude as to simulate the inertness of sleep. 
 But if the top be suitably constructed, it will be by 
 no means lifeless, but will betray its veiled activity 
 by its hum. Here arises another question to be 
 looked into. Of what nature are the vocal organs of 
 the top by which it sings its own peculiar and mo- 
 notonous song ? If we were to spend as much time 
 upon this subject as would be required to do it proper 
 justice, we should get but little change out of a whole 
 evening. In this, therefore, as in so many other cases 
 which we have been obliged, for like reasons, to treat 
 in a similarly incomplete manner, it must suffice to hint 
 the general nature of the answer, leaving the details to 
 be ascertained by any enterprising inquirer. 
 
 What we call sound is our perception, through our 
 
250 
 
 children's toys. 
 
 ears, of rapid vibrations. These are usually those of 
 air, though the quivering motion is more perfectly con- 
 veyed by other substances. The stethoscope, for ex- 
 ample, an instrument used for the medical examination 
 of people's chests, is a wooden tube which catches 
 sounds which, without its intervention, would not be 
 audible, and transmits them, with great fulness, deli- 
 cacy, and clearness, as thrills, running along its own 
 person, to the ear of the listener. The pitch of any 
 note depends exclusively on the rapidity of these 
 vibrations ; that is to say, the greater the number of 
 them which take place within any given period of time, 
 as, for example, a second, the higher the note. Such 
 vibrations may be properly regarded and spoken of as 
 waves, since they behave as such, and sound will be 
 rightly understood if it be considered as a ripple. A 
 ripple of water is, indeed, confined to one plane, that 
 is to say, it takes place along one flat surface only, 
 while billows of sound are spherical, that is, are pro- 
 pelled in all directions from their origin, like rays 
 of light from a star. But this point of difference 
 between the two cases may be quite disregarded 
 as far as the purposes of the present moment are 
 concerned. 
 
 Sound, then, being viewed as a ripple, it will be 
 true that the shorter the waves, that is to say, the 
 greater the number of them which could be arranged 
 as a series within any given longitudinal space, the 
 higher the pitch of the note which they form. On the 
 other hand, the loudness of any given note, which, as 
 need not be observed, is quite another thing altogether 
 from its pitch, does- not depend on the thickness of 
 
childeen's toys. 
 
 251 
 
 the individual waves measured through from back to 
 front, but on their height, or, to put the same thing 
 another way, on the depth of the valley which inter- 
 venes between any one of the tiny billows and its next 
 neighbour. 
 
 Whatever musical instrument be employed, the 
 notes are, in fact, generated by the same identical 
 means, that is to say, by the production of vibrations, 
 or waves, although the tackle employed for the pur- 
 pose varies according to the character and quality of 
 the sounds which are wanted. When the piano is 
 played, string after string is set vibrating by a series 
 of blows from little mallets worked from the key-board. 
 A harpist employs the direct agency of his own fingers, 
 and instead of hammering the chords, he plucks them. 
 Wind instruments, also, are simply implements for 
 communicating vibrations to air. It is interesting to 
 note the variety of mechanisms by which the desired 
 result is attained in the several components of an 
 orchestral band, taking as typical examples of different 
 leading methods — say — the trumpet, oboe, drum, harp, 
 flute, and clarionet. To these may be added a home- 
 made and simple imitation of human speaking tackle 
 constructed of two tubes, one of glass, and the other 
 of india rubber. The latter is to be arranged so as to 
 clasp the former very tightly for a short distance of its 
 length at either of its extremities, and should project 
 an inch or so beyond it. By blowing down the glass 
 tube in such a manner as to impart to it a thrill, or 
 shiver, (the knack of accomplishing this is one which 
 cannot be described or taught in words but is only to 
 be learnt by experiment,) sound is produced, and by 
 
252 
 
 children's toys. 
 
 then elongating the elastic mouth-piece in varying de- 
 grees by stretching it, a very fair imitation of the action 
 and effect of the lips in modulating the voice may be 
 achieved. The organ supplies an example of the 
 creation of notes by more than one method, that is to 
 say, by stopped and by open pipes of peculiar construc- 
 tion. For our present purposes a flute will supply the 
 most appropriate illustration of the generation of sound, 
 since its notes are born of parentage which has a close 
 relationship to that of which the hum of the humming 
 top is the offspring. 
 
 A flute, to describe it in its main aspect, is, as 
 everybody knows, a hollow cylinder open at one end 
 and closed at the other, and having near one of its 
 extremities a hole to which the mouth of the player is 
 applied. We need not deal here with the various 
 accessories of the instrument. If we were to do so we 
 should have to include among them, as being the most 
 important of all, the lips of the performer, since these 
 are not mere sources of air, but in reality integral and 
 essential parts, for the time being, of the instrument 
 itself, since it is on their texture, and mode of employ- 
 ment, that the quality of the notes chiefly depends. 
 Hence it is that the tone of one and the same flute is 
 found to vary from that exquisitely limpid clearness 
 which to the sensations of any competent judge is the 
 most delicious sound, as coming nearest to the supreme 
 perfection of the human voice, which can be produced 
 by any musical instrument, but which is extremely 
 rarely heard, down to the usual husky, cold-in-the-head 
 sort of snuffle with which we are all, unhappily, but too 
 familiar. 
 
childebn's tots. 
 
 253 
 
 Now the performer must blow across the hole which 
 has been spoken of, and not into it. When he does 
 so, a wave of air is set going, which runs along the 
 interior of the hollow body of the flute towards its open 
 end, and thence returning, partly interrupts the blast 
 flowing from the lips for an indefinitely short instant of 
 time. This proceeding is constantly repeated, and a 
 series of waves thus going and returning, and eventu- 
 ally issuing from the mouthpiece in the form of small 
 puffs, and vibrations, constitutes sound. Why the 
 mouthpiece should be placed where it is, and how it is 
 that the waves should conduct themselves as has been 
 described, coming back from the open end instead of 
 escaping from it — these, and a number of other phe- 
 nomena which must be thoroughly studied before the 
 action of a flute can be properly understood, are not 
 such as can be entered upon here. They must perforce 
 be left as mere matters of bare statement. 
 
 If a flute were to be made to spin, or to move through 
 the air in any other manner, with sufficient rapidity, which 
 would have to be very great indeed, it would give forth a 
 sound, because, as we had occasion to observe some time 
 back, with reference to a windmill supposed to be carried 
 on a railway train, it is the same thing in effect whether 
 air is in motion and the object on which it acts is at rest, 
 or whether what may be called a reversed counterpart 
 of this arrangement prevails, since in both cases a cur- 
 rent, either actual or virtual, is produced. The note 
 uttered by a flute made vocal by the consequence of 
 its own motion would be but a dull monotone, since 
 it would neither be turned out duly clear and fresh, 
 nor could it be inflected, for the lips and mechanical 
 
254 
 
 children's toys. 
 
 appliances which are indispensable for giving deci- 
 siveness and variety would be wanting. It would be 
 thus, in fact, a simple buzz, or whirring sound. 
 
 It has been stated that a flute may be made to speak 
 by putting it into a certain relation with the air about it 
 equivalent to, but not absolutely the same as, that which 
 prevails when it is played in the orthodox manner. Its 
 vocal faculty is hence seen, or may be at any rate sur- 
 mised, to have the same organization as that of a top. 
 It maybe still more readily caused to discourse articulate 
 music by substituting for the lips of a player a vibrat- 
 ing tuning fork, and by executing at the same time 
 the fingering which properly belongs to the note which 
 is thereupon sounded. The secret of the hum of a top 
 now stands revealed. 
 
 It is as well to give a word of caution against con- 
 fusing the droning song of a humming top with that 
 which is heard on applying the ear to a shell. A hasty 
 and erroneous assumption might be made that as a top 
 and a shell seem to the ear to sing the same kind of 
 song, therefore their organs of speech, and sources of 
 voice, are alike, which is not at all the case. A top 
 draws breath, and becomes vocal, through its own mo- 
 tion, in the manner which has been attempted to be 
 described. The note of a shell is a mere tumultuous 
 combination of the echoes of external noises, many of 
 which would be individually too weak and slender to 
 announce themselves separately to our perceptions, 
 human organs of hearing not being sufficiently fine- 
 strung to deal with sounds not possessing a certain de- 
 gree of strength and fulness. When, however, these 
 external noises become blended by the shell into one 
 
childken's toys. 
 
 255 
 
 general chorus, they then acquire sufficient body and 
 substance to proclaim their existence, since the tiny 
 waves of which they are severally composed, beating 
 against the drum of the ear in the shape of a general 
 and confused torrent, are thence translated to the 
 brain, which is the real seat of hearing, as an undefined 
 and continuous hum. A shell " roars/' as it is ex- 
 pressed, in this way because it possesses in an eminent 
 degree the faculty of resonance, that is to say, the con- 
 formation and texture of its interior surface happens 
 to be such as to render it intensely responsive to sound. 
 
 Nature, who is a skilled artificer of much resource, 
 has availed herself, in the formation of the human organs 
 of speech and hearing, of all the principles found ser- 
 viceable in the construction of the musical instruments 
 which have been named this evening, but with far more 
 efficient and delicate modes of application. Being thus, 
 as might be expected, aware of the faculty of resonance 
 with which shells are gifted, she has turned it to ac- 
 count in the structure of the ear, for we find that what 
 is called the " cochlea," or u shell," is an important con- 
 stituent of our arrangements for hearing. There is an 
 odd conception which children and amusingly ignorant 
 people entertain, that the hum of a shell resides in some 
 way or other within its chambers. They have a hazy 
 sort of notion that the roar of the ocean in which, as 
 they suppose, the fish who was lately occupier of the 
 tiny marine villa which is now hollow and echoing 
 passed his existence — (he may probably have lived in 
 depths which were still and silent enough) — became so 
 inveterate a frequenter of his premises as to continue 
 to haunt them after his decease, and when far removed 
 
256 
 
 children's toys. 
 
 from winds and waves. This theory is put out of Court 
 by the fact, which is easily substantiated by experiment, 
 that any object which happens to have by means of its 
 form, and the mechanical conditions of its substance, 
 a special faculty for yielding resonant echo, will roar 
 vivaciously, although it may have been always inland. 
 
 Bar-trumpets, such as deaf people use, act to a great 
 extent in the same manner as shells by reflecting and 
 concentrating sound. They are not properly to be re- 
 garded as the converse of speaking trumpets, since they 
 are the very same things, only that as their purpose is of 
 a different kind their shape and mode of employment 
 is appropriately, but slightly, varied. It 'will be re- 
 marked that ever so loud a sound does not produce a 
 blast like that from a military trumpet in a deaf person's 
 ear. It would be highly inconvenient if it did so ; and 
 there are two reasons why no such effect takes place. 
 One of these is that such a note is not produced, or 
 producible, by mere sound, that is to say, by air in 
 motion, however energetic. A trumpeter by means of 
 his lips sets the metal substance of the trumpet vibrat- 
 ing in concert and conjunction with the pulse of the 
 column of air which gives the note, thus intensifying 
 its motion and effect. Without the thrill which must 
 be imparted to the instrument by the lips through direct 
 contact between it and them, the note of a trumpet or 
 of any wind instrument cannot, as a general rule to 
 which the exceptions are limited, be generated with 
 either the body, strength, or precision which are all of 
 the very essence of its being. It will be observed, 
 moreover, that by blowing through the mouthpiece of 
 a trumpet the whole effect, whatever it may be, of this 
 
children's toys. 
 
 257 
 
 act is applied to the instrument. On the other hand, 
 when speaking or shouting takes place at the bellshaped 
 end of a speaking trumpet, many of the vibrations of 
 air escape laterally, or at any rate are not projected 
 through the resonant channel with all the original 
 energy which they may happen to possess. 
 
 To return to our top, which is all this time hum- 
 ming in its sleep. Its energy of spinning, and the 
 tendency, which is wholly dependent on that energy, 
 to maintain an erect attitude, are both, slowly perhaps, 
 but surely, undermined by two forces, namely, that of 
 friction at the spot on which the peg stands, and the 
 resistance of the air. In real truth the resistance of 
 the air is as simply friction, and nothing else, as is the 
 grind by the point of the top's peg upon its support. 
 Could, which is practically impossible, a perfect vacuum 
 be formed, that is to say, could air, and everything else 
 which can occupy space, be exhausted from some close 
 chamber, and could, which is also impossible, friction 
 be prevented from occurring at the tip of the toe on 
 which the top pirouettes, the spinning would literally 
 go on throughout all eternity, for there would then be 
 no reason why it should ever stop. The supposition 
 that it either would, or could, come to any end, except 
 under compulsion, is fully as inconceivable as that of 
 its commencing of its own accord, since both of such 
 proceedings would equally imply the exercise of spon- 
 taneous action on the part of the top, that is to say, the 
 possession on the part of a piece of wood of an inde- 
 pendent will of its own, and of a muscular apparatus 
 capable of giving effect to mental impulses. 
 
 We spoke some time ago of what is called " vis 
 
 s 
 
258 
 
 childken's toys. 
 
 inertia/' meaning the indisposition on the part of any 
 object to move unless under the impulse of some ex- 
 ternal force. The fact seems to be usually overlooked, 
 or taken less account of than it should be, that the vis 
 inertiaa continues with unimpaired effect when the re- 
 pose of the object in question is broken, and motion is 
 substituted for quiescence. For the moving thing still 
 retains its quality of inertness quite undiminished, 
 that is to say, it is as passively disposed as ever, and 
 thus has no sort of tendency either to increase the 
 speed with which it is now endued, or to relax it, ex- 
 cept, as has been stated, under the action of some ex- 
 ternal force. Not voluntarily stopping, therefore, but 
 when the life of its impetus has wasted itself in battle 
 with enemies, the top becomes gradually amenable to 
 the attraction of gravity only. This force, endeavour- 
 ing, as is its wont, to lay things as low as they can go, 
 aggravates each of the slight, and at first imperceptible, 
 declinations from the exact perpendicular which small 
 disturbing influences, such as the irregular action of 
 currents of air, and of friction, are sufficient to cause. 
 The power on the part of the axle of the top of recover- 
 ing an erect posture is enfeebled more and more by 
 every such strain on its supports. The operation of 
 these occult influences is first declared by a momentary 
 dip on one side or the other which is shortly afterwards 
 repeated in the aggravated form of a resolute " duck " 
 downwards. Presently the axle becomes altogether 
 tottering, and eventually a dive is made which is deep 
 enough to allow some point of the under side of the 
 body of the top to graze the ground. The force of 
 friction which is generated by the collision instantly 
 
children's toys. 
 
 259 
 
 engages in violent conflict with snch of the spinning 
 motion as yet survives, and in the short, but sharp, 
 contest which ensues the top is carried hither and 
 thither in convulsive throes, till it comes to rest on its 
 side, still, and inanimate. 
 
 It lies, as has been said, altogether lifeless, but this 
 does not imply that its inertia is the result of the sus- 
 pension or destruction of all agencies tending to produce 
 motion. By no means. The top is at this moment 
 fully as much u a creature of impulse " as it was when 
 in full spin. If caused to poise on the tip of its peg, 
 but without revolving, it is in a position of what is 
 called " unstable equilibrium/' for although the result 
 of the forces which control it is such as to produce rest 
 for the moment, the mutual adjustment of these agencies 
 is of a kind which not only does not recover itself if 
 ever so little disturbed, but has a tendency to produce 
 still further motion. Sleeping on the point of its peg, 
 it is in a position of temporarily stable balance, its 
 quiescence of attitude being due to forces which, while 
 producing a motion of its parts round its axis, do not 
 cause, or favour, but oppose, any transference of its 
 mass as a whole from one posture or place to another. 
 A state such as this, is, as has been said, one of what 
 the French call " equilibrium mobile/ ' or " kinetic 
 stability/' as it is sometimes termed with us. Lying 
 on its side, the top is in a position of what may be 
 termed " neutral " equilibrium, since its rest is per- 
 manent until broken by the entry on the scene of some 
 altogether new force. When this event occurs, as, for 
 example, if it is rolled along the floor, the recumbent 
 top yields itself passively to compulsion^ but when 
 
260 
 
 childeen's tots. 
 
 relieved from the control of this fresh power, it is not 
 impelled to move farther, or to reinstate itself in its 
 original place. 
 
 There is not, however, in its present condition or, 
 as far as we know or believe, in that of anything any- 
 where in the Universe, either now, or since Time was, 
 or will there ever be till Time ends, real and absolute 
 rest, in the sense of the cessation of all forces tending 
 to produce motion. The repose which the top now 
 exhibits is merely the result and sign of a balance 
 between certain pressures having been set up. The 
 top is giving what may be regarded as a sustained 
 blow upon the floor, since the pressure exerted by its 
 weight is a push, and a push is a more or less pro- 
 tracted stroke. Or if this view of the situation be 
 found difficult of apprehension, it may be said that the 
 top is doing, by the pressure of its weight, what is 
 equivalent to giving a continued series of infinitely 
 small knocks upon its point of support. If the weather 
 were hot, and the top were of butter, so that it had no 
 fixed rigidity of form, the presence of the forces which 
 are in action upon it would stand revealed. For its 
 body and peg would subside into a mere lump. But 
 this alteration of form would not, as you know, be 
 automatic, but could only be due to active external 
 agencies. 
 
 The observation which was accidentally called forth 
 that complete quiescence, in the sense of the establish- 
 ment of an armistice between various contending forces, 
 such as gravity, and others, which are unremittingly at 
 work throughout Creation, is a state which is unknown, 
 as far as we can tell, to the material Universe which 
 
children's toys. 
 
 261 
 
 surrounds us, may be made more full, and you will not 
 grudge the bestowal of a moment on the reflections 
 which it occasions, although these are not directed to 
 any question which is immediately before us. 
 
 It was remarked that the stillness of a top whose 
 span, or spin, of life is over does not indicate that its 
 person has ceased to be the bone of contention to 
 warring forces, but merely that a balance of a stable 
 nature has become established between the antagonisms 
 which are still at work upon it, and that absence of 
 motion is the consequent result. This quietude, as it 
 may be well to repeat yet once more, in order that the 
 statement may be pushed well home to attention and 
 remembrance, does not by any means show or imply 
 that the strife of unseen agencies has ceased, but 
 merely that these have come, as it were, to a position 
 of deadlock. Not only, it may be added, does the 
 activity of the multitudinous hosts of forces which are 
 at work throughout the Universe never fail or inter- 
 mit, but actual motion, so far as we can see or con- 
 jecture, never ceases for one instant in even a single 
 particle of matter in the most retired and remote 
 corner of the whole domains of illimitable space. 
 
 What, for example, is the leading type and symbol of 
 everlasting rest, and immobility, according to popular 
 notions ? If an inventory were to be taken of Nature's 
 furniture, a mountain would certainly be put down 
 among the substantial fixtures. To our perceptions, 
 no doubt, it is a sedate object enough, sitting compos- 
 edly, as is natural to people of the fat habit of body which 
 distinguishes it, on its broad and fixed base. But could 
 we examine it closely, we should assuredly find that it 
 
262 
 
 children's toys. 
 
 is endued with an abundance of what is called molecu- 
 lar motion, that is to say, that its every atom is in cease- 
 less and energetic vibration, and not only that, but 
 unrestingly shifting its position. There is abundant 
 evidence of the clearest kind that motion of this sorb is 
 never suspended, although the distance traversed by 
 the particles in their journeys are too minute to be ap- 
 preciable by the human eye. So much for the parts. 
 As for the mass as a whole, it is, as we know, scudding 
 round the Sun upon the Earth, on which it is set like a 
 stud. Moreover it whirls round the Earth's axis as well 
 as progresses in the terrestrial orbit. 
 
 It may have, and no doubt has, countless other mo- 
 tions. For our Sun has been detected to be a mere 
 planet, who, with, of course, the whole attendant solar 
 system, revolves, probably, round a certain Pleiad called 
 Alcyone, one of the stars in the Milky Way. We con- 
 jecture this to be the case, because if there be anything 
 whatever in the Universe, which, as far as our percep- 
 tions enable us to judge, is fixed, it is the star which has 
 just been mentioned. It is thought that our Sun with 
 his attendant satellites circles round Alcyone, and that 
 he takes about eighteen million years to complete the 
 " grand tour." However that may be, it has been 
 proved to absolute demonstration that our Sun is not 
 rooted to one spot, as w T as formerly believed. He, and 
 with him, ourselves, are all bound for a point in the con- 
 stellation Hercules, towards which, if Sir J. Herschel is 
 to be believed, we progress at the rate of about four 
 hundred and twenty-two thousand miles a day. If, as 
 is probably the case, Alcyone, though its motion is 
 beyond our ken, is, in real truth, a mere planet, like our 
 
CHILDREN* S TOYS. 
 
 263 
 
 Earth, the sun round which it revolves is some stu- 
 pendous globe so immeasurably remote from us that the 
 most vigorously excursive imagination gets spent and 
 wing-weary in the abortive attempt either to reach or 
 picture it. And this great star, again, is, as likely as not, 
 a mere subordinate member of some larger system of 
 celestial bodies, and is dominated by some one individual 
 of a series of gigantic orbs whose distances and vastness 
 are such that the mind gains nothing more by an attempt 
 to bring them within the range of definite conception 
 than a general sense of mere bewilderment and fatigue. 
 
 We have thus no reason to suppose that there is 
 anything in the universe which continues in one and the 
 same station. As far indeed as we can infer from the 
 knowledge which we possess, it is not likely that the 
 order of Creation, being such as it appears to be, permits 
 a single one of the unnumbered multitude of stars which 
 crowd our sky, or of those which, as it may be, people 
 the abysses of boundless Space beyond with thronging 
 millions upon millions which, as being endless, no 
 figures could count, to halt for one instant. Gravitation, 
 to whose range of influence there are no known or 
 conceivable limits, would, if it were not counteracted 
 by motion, as it is, in the case of the Earth, by our 
 planet's waltz round the Sun, instantly disorganize the 
 whole arrangement of the heavenly hosts, drawing them 
 together, and eventually pounding them up against 
 one another in a grand general milee and collision, 
 after which the fragments would be burnt up by the 
 heat generated by the clash. If however the Tory-like 
 characteristic of absolute immobility could with any 
 sort of plausible reason be attributed to even a single 
 
261 
 
 children's toys. 
 
 one of the multitudinous denizens of space, such an orb 
 would still present no exception to the general stir 
 which seems to pervade the Universe, unless, in addition 
 to its permanent tenancy of one and the same parti- 
 cular location, it were also devoid of revolution on its 
 axis, and remained, moreover, in one unchanging atti- 
 tude, and with no alteration in the disposition of its 
 component parts. 
 
 The truth thus comes into view that rest can mean 
 nothing more than that the body which is said to be 
 in that condition is merely maintaining an unaltered 
 position and attitude with reference to the person who 
 is describing it. If you go from London by one of 
 the railways which pass through Clapham Junction, it 
 not infrequently happens that as there is a great 
 multiplicity of trains always going by the same route, 
 and in the same direction, you may find yourself in a 
 carriage which is travelling at equal speed with another 
 which is proceeding alongside of yours on a parallel 
 line of rails. To you the other carriage is apparently 
 stock-still, as much so as the interior of the com- 
 partment in which you sit, and for the same reason, 
 since, with relation to yourself, there is no change of 
 position. In this limited and relative sense only does 
 rest exist ever or anywhere in the perpetual stir and 
 whirl of the big bit of intricate machinery which we 
 call the Universe. 
 
 To return to tops. There is a very convenient form 
 of the toy which is made in the shape of an inverted 
 cap, and has a very short peg to stand upon. It must 
 therefore be poised with the point of the toe of its 
 wooden leg in a shallow hole scooped at the top of a 
 
children's toys. 
 
 265 
 
 steady post, so that the edge of its body, or what may 
 be called the skirts of its dress, may not touch the 
 table. It overhangs the top of the post all round, and 
 its centre of gravity being thus below its point of sup- 
 port, the forces to which it is amenable tend as a whole 
 towards the maintenance of its existing upright pos- 
 ture, so that it will balance on its toe not only when 
 spinning, but when quite still, recovering itself after 
 being made to sway in any direction. The stability of 
 its equilibrium is plainly to be accounted for on the same 
 grounds as those on which the balancing on the point 
 of a pin of a cork, when fitted out with two forks, was 
 explained just now. Knowing, as we do, something of 
 the conditions by which the hum of a top is generated, 
 it need hardly be remarked that an open hemisphere, 
 such as that which has just been described, must neces- 
 sarily be mute. It might easily, however, be rendered 
 vocal, if that were desired, by a slight modification of 
 its form. 
 
 Tops are frequently equipped with appliances for the 
 production of " chromatic effects," that is to say for 
 the display of optical phenomena of colours. Small 
 discs of paper coloured in various ways, some irregu- 
 larly, and some in symmetrical patterns, are supplied 
 for use with a toy of this kind. Each of these is pierced 
 with a hole at its centre, so that it slips readily over 
 the spindle, and rests on the body of the top, whose 
 upper surface is made flat so as to afford suitable ac- 
 commodation to it, and afterwards to its fellows, which 
 are to be laid in turn one upon another, thus giving a 
 succession of different effects. The top having been set 
 spinning, any disc which is dropped into the place 
 
266 
 
 children's toys. 
 
 arranged for its reception acquires at once a similar 
 movement of revolution. This is so because its sur- 
 face being in contact throughout its whole extent with 
 that of the stage on which it reposes, and which is in 
 rapid motion, its quiescence, or indeed any difference 
 of speed in the revolution of the two bodies which are 
 thus brought together, would be vehemently opposed 
 by friction. 
 
 The first disc which happens to come to hand 
 is, we will say, one which is marked with irregular 
 plots of colouring. On dropping it over the spindle, it 
 instantly produces, as will be seen, a brilliant varie- 
 gated device resembling a rainbow, or target, in gen- 
 eral effect, but possibly not constituted of the same 
 hues ; or if of the same, not, perhaps, arranged in a 
 similar sequence to that in which they are disposed in 
 either of those objects. The patterns which may be 
 thus displayed in absolutely endless variety, are all, as 
 will be at once understood, due to the persistence of 
 vision which was so fully discussed when the principles 
 with which the zoetrope is concerned were discussed. 
 
 You will recollect the cards which were then also 
 examined, furnished, severally, with a device purposely 
 left incomplete on one face, the complementary details 
 being supplied on the other. They were to be spun, as 
 you will remember, in order that the persistence of 
 vision, when thus called into action, might bring to the 
 front the divided halves of each picture in rapid alter- 
 nation, so that they should coalesce into a perfect whole. 
 The cards in question may be conveniently used in con- 
 junction with a top, for the latter thus imparts the 
 necessary spinning to them. A pin so placed as to 
 
children's toys. 
 
 267 
 
 traverse the face of one of the cards and pass across its 
 centre is substituted for the strings used in the former 
 case, and a small portion of the free length of this trans- 
 verse axis, or axle, for it may be described by either of 
 these terms, which is continued beyond the edge of the 
 material to which it is attached, is inserted in a hollow, 
 or sheath, formed in the head of the top. The mode in 
 which this arrangement acts, and the nature of the re- 
 sults which it accomplishes, are sufficiently obvious. 
 
 Like effects, and for similar reasons, are produced 
 by narrow strips of foil, glass, or other stiff material, of 
 designed shapes, for when made to spin by having their 
 lower extremities planted in the crown of the spindle of 
 a revolving top, they represent miniature goblets, or 
 hats, or any other objects of which the opposite sides 
 have a corresponding, though reversed, contour of 
 outline. 
 
 In taking leave of the subject of tops it may be 
 remarked that the familiar lines — 
 
 " A primrose by the river's brim 
 A yellow primrose was to him, 
 And it was nothing more " — 
 
 would be applicable, in the sense which they are in- 
 tended to have, to anyone who were to view this toy 
 as a mere simple plaything, easily to be understood, and 
 fit for no better service than that of affording a limited 
 degree of amusement, and that too of a very humble 
 order, to a child. So far is this from being the truth, 
 or anything like it, that a top may be employed in ex- 
 hibiting a multiplicity of interesting and beautiful ex- 
 periments in Science. Moreover, anyone who is capable 
 
268 
 
 childken's toys. 
 
 of giving a really accurate and full elucidation of the 
 secrets which its motions involve mast be an astrono- 
 mer, or at any rate already equipped with much of the 
 knowledge and capacity which go to the making of one. 
 Such a person, for example, would necessarily be com- 
 petent to elucidate what is called the " Precession of 
 the Equinoxes," a term which reminds one, and not 
 without reason, of "a terrible man with a terrible name" 
 who figures in Southey's " March to Moscow." For 
 the expression, which has a sound which seems to give 
 warning of perplexity, represents a formidable problem 
 of astronomy of considerable importance, but so in- 
 tractable that even Sir Isaac Newton failed to make it 
 quite clear, and it was not thoroughly explained until 
 after his time. 
 
 The celebrated mathematician Buler, who lived about 
 a century ago, devoted a whole book to discussing the 
 motions of tops. He also wrote a treatise on kites. 
 The mention of this latter circumstance is a reminder 
 that kites are awaiting our notice. 
 
CHAPTER XL 
 
 N the hands of an ingenious and well in- 
 formed person a kite is a toy which, by- 
 suitable adaptations, may be made to do all 
 sorts of things, and among these to talk 
 that is to say, its various modes of behaviour under 
 different circumstances, and under different modifica- 
 tions of its structure, will speak a suggestive and 
 interesting language to those who can construe it. 
 Kites, like the great majority of other common things 
 which are about us in the world, are, as Pindar con- 
 cisely expresses it, " (jxovavTa (tvv€tol<ti," that is to say 
 "have a voice for the wise." Sir Isaac Newton seems 
 to have gained most of his early lessons in Science 
 from kites. 
 
 The first question which naturally arises, that, 
 namely, of why it is that a kite ascends, will be easily 
 solved by the simple process of considering what the 
 forces operating upon its surface are, and then find- 
 ing what must be the outcome of their simultaneous 
 action, which will be done, of course, by the parallel- 
 ogram of forces. The use of the tail is to pull down 
 the lower extremity of the backbone of the kite so as 
 
270 
 
 children's toys. 
 
 to prevent the head from butting, as it were, against 
 the wind, which it would otherwise inevitably do, for 
 just the same reason, as will be apparent on a moment's 
 consideration, that in a weathercock the point of the 
 vane turns to the breeze. By the drag which the tail 
 exerts the surface of the kite is kept fair to the wind 
 at any desired inclination. It may be mentioned that 
 the best results are produced when the angle made 
 with the wind by the part of the backbone of the kite 
 which is above the point of attachment of the string is 
 one of rather more than 54 degrees. Nobody, proba- 
 bly, would reason with such extravagant unreason as 
 to suppose that the gossamer-like buoyancy of the 
 materials of which the tail is usually composed pro- 
 motes the ascent of the kite by something of a lifting 
 effect. The tail of a horse, though consisting mostly 
 of hair, and being therefore light in proportion to its 
 bulk, does not help the animal to raise his hind quarters 
 when he wants to kick, and it was not placed where it 
 is found, for any such purpose. The movement upwards 
 of the kite is of course opposed by the downward drag 
 of the weight of the tail. This drawback, however, as 
 we have already seen, is more than compensated by 
 the increased support which the kite derives through 
 being kept in such an attitude that the force of the 
 wind is exerted upon it to the fullest mechanical 
 advantage. 
 
 If, as may be asked, the main use of a tail con- 
 sists simply in its weight, why should not an equiva- 
 lent in the shape of a bit of lead, scaling at an ex- 
 actly similar number of ounces or drams, and attached 
 to the bottom of the kite's backbone, or suspended 
 
children's toys. 
 
 271 
 
 thence by a string, answer the same purpose quite as 
 well ? If it were the habit of a kite to poise motionless 
 in the air, what may be termed the operative element 
 in its tail, or, in other words, its heaviness, might, no 
 doubt, be condensed, as suggested, into the length of 
 an inch or less. But owing to the constant variations 
 in direction and power of the current or currents of air 
 by which a kite is sustained, and to the ever-changing 
 balance of the ot herforces to which its movements 
 are amenable, its station and attitude alter more or 
 less with every moment. A little observation of the 
 action, of the tail will show that this appendage is so 
 constructed as to moderate by a constant and effective, 
 but always temperate and gentle, resistance, any excited 
 behaviour on the part of the kite, with a persuasiveness 
 which answers its purpose much better than the rough 
 correction which a weight jerked and joggling irregu- 
 larly in the air would apply. 
 
 The paper bobs which are arranged in a series along 
 a string, and which form the tail, have in the aggre- 
 gate a surface which is considerable in itself, and which 
 is very large in proportion to their weight, so that 
 the air exercises no little opposition to their motion 
 in any direction. Owing, also, to their lightness, 
 they acquire no appreciable momentum, which in this 
 case would be a force tending to disorder. Since, 
 however, the resistance on the part of the atmosphere 
 is largely multiplied with every degree of increase of 
 the velocity of a moving object, the drag of the whole 
 tail becomes proportionately heavy as the exigencies of 
 each moment may demand, so that it operates with 
 something like the calculated effect of an elastic spring 
 
272 
 
 children's toys. 
 
 so constructed as to deal with, varying alternations of 
 pressure with a vigour corresponding in energy with 
 every stress of strain which it may be called upon to 
 encounter. 
 
 Kites may be made in an infinity of forms. To de- 
 termine which kind will fly best would require more 
 consideration than we can bestow upon the question 
 just now. It would be difficult however to improve 
 upon the most popular existing form, that, namely, 
 with the round head, and the body tapering down into a 
 point, for the adoption of this figure is based upon sound 
 principles which will become apparent upon a little 
 consideration. 
 
 Whatever the kite may be in its own person, much 
 will depend on the right selection of the exact point 
 where the string is to be attached to it. If this be not 
 successfully hit, the kite will either exhibit a dull list- 
 lessness in ascending, or will perform wild and undigni- 
 fied antics by diving, or whirling round and round, like 
 an acrobat turning somersaults, and may eventually, 
 perhaps, put a suicidal end to its own existence by 
 plunging downwards upon its head, and snapping the 
 bow of its frame. The precise situation of the critical 
 point in question, which, thus becomes so necessary to 
 be ascertained, will be readily determined by experi- 
 ment. In the first instance, the spot where the string 
 is to be attached may, for the purpose of starting with 
 some rough approximation to its proper whereabouts, 
 be taken to be a little above the middle of a straight 
 line drawn from shoulder to shoulder of the kite across 
 its chest. If the kite be now suspended from the string, 
 it will, or at any rate should, hang evenly balanced in 
 
children's toys. 
 
 273 
 
 respect of its two sides, but with its head a little higher 
 than the tail of its backbone. Presently, when cricket 
 bats come under examination, it will be necessary to 
 revert for a moment to this question of the place where 
 the string should join the kite, and it will be convenient 
 to adjourn what little remains to be said upon the sub- 
 ject to that occasion. 
 
 Before quitting, however, the general subject of 
 kites, it may interest those to whom the information may 
 be new to hear that the services of these toys were en 
 listed by the American philosopher Franklin in deter- 
 mining the real nature of lightning, which had not been 
 understood until elucidated by his experiments. By 
 flying a kite, and manoeuvring it into a thundercloud, he 
 tapped, as it were, the sky, and ran off its charge of 
 lightning down the string into a receptacle where the 
 electric fluid could be subjected to analysis. The string 
 thus became an embryo conductor and electric telegraph 
 also. The result of the experiments was to establish 
 the fact, which had never been previously verified, of 
 the identity of lightning with the electricity which may 
 be generated by a machine. 
 
 In the old heathen mythology Prometheus is repre- 
 sented as stealing a spark from Heaven and bringing it 
 to Earth, when Jupiter, like a late Chancellor of the Ex- 
 chequer with his intended tax upon matches, had sought 
 to deprive mortals of the benefits of fire. The modern 
 Prometheus, Franklin, who not only stole thunderbolts, 
 but showed that they were of a material by no means 
 exclusively celestial, but were such as anybody could 
 manufacture with some simple tackle of glass and silk, 
 would have fared even worse than his prototype did, 
 
 T 
 
274 
 
 childken's toys. 
 
 according to the classical legend, if he had lived in 
 mythological times, but Jupiter's day was over before 
 America was discovered. 
 
 It was intimated just now that a kite and a cricket 
 bat, though they might be supposed to be unlikely to 
 have anything in common, present a point for consider- 
 ation which occurs in both. If a cricket ball, or any 
 hard, or resisting, object, be struck by the extreme 
 end of a bat, everybody knows by experience the odious 
 jar which a blow so given creates, sending as it does 
 a painful shudder, like a shock from a galvanic battery, 
 up to the elbow. The same sort of " unpleasancy " 
 (to adopt a word from the vulgar tongue) occurs if the 
 ball meets the bat just below the handle. Stinging 
 sensations of the kind which has been described are 
 familiar to anyone who has ever used a hoopstick. A 
 sword, which would readily cleave an object meeting 
 its edge at or near one particular point in its length, 
 might be probably itself shivered, yet without accom- 
 plishing its intended task, if set to make a cut with a 
 part of the blade close to either of its extremities. A 
 knock given by mischance by the neck instead of by 
 the head of a hammer might go far towards breaking 
 the handle, but would be almost altogether devoid of 
 effect upon the nail. 
 
 On the other hand, there is one exact point, and 
 one only, situated, roughly speaking, at about three 
 quarters of the way from the handle to the other end 
 of a bat, hoopstick, or sword, or, in the case of a 
 hammer, in its head, at which the striking implement, 
 to achieve the best effect which it is capable of pro- 
 ducing, should deliver its blow. This point is called 
 
childeen's toys. 
 
 275 
 
 <c the centre of percussion," and the instrument which 
 gives the blow will therefore be conveniently de- 
 nominated as "the percutient body." The centre of 
 percussion is that spot at which the whole momentum 
 of the percutient body is, as it were, concentrated. 
 
 The question why it is that a bat, or sword, or other 
 percutient body, does its most efficient work under 
 certain very precise conditions, only, which are easily 
 ascertainable, and that a kite also flies its best when, 
 and only when, the string is attached to it at a spot 
 which is in fact its centre of percussion, is an interest- 
 ing enquiry, and one of no great difficulty. To discuss 
 it properly, however, at this moment would take too 
 much time, so that it must be remitted to the category 
 of matters which are suggested to you as worth ex- 
 amination at your leisure. To get hold of the matter 
 properly, it will be necessary, as you will perceive, to 
 consider the several different modes in which a percu- 
 tient body may move, and what would be its centre 
 of percussion in each case. It will be found that the 
 centre of percussion must shift its place with every 
 change in the manner in which the percutient instru- 
 ment strikes. The centre of percussion, for example, 
 of an object flying freely in any direction through 
 space, and having a movement purely of translation 
 and altogether exclusive of revolution, would be found 
 to be necessarily in the line in which its centre of 
 gravity is travelling. This would be the case with a 
 bar of iron of uniform thickness and weight through- 
 out its whole length, and projected through the air in 
 the manner just described. If the same bar were to 
 swing from one of its ends, as from a hinge, or other 
 
276 
 
 children's toys. 
 
 fixed point of attachment, its centre of percussion 
 would be found to fall between the middle of its length 
 and its free extremity. The centre of percussion would 
 thus be further from the axis of movement than the 
 centre of gravity, which latter must obviously be half 
 way along the bar. 
 
 Compound motions like those of a bat, a hoop- 
 stick, or a sword, which are a combination of such as 
 have been mentioned, bring the centre of percussion 
 to some spot which is determined by the precise con- 
 ditions under which the action of the percutient in- 
 strument takes place, that is to say by the manner 
 in which it is wielded, whether with a sweep or ham- 
 mer-fashion, and by the situation on its length of the 
 place where it is held, or whence it is swung. 
 
 The centre of percussion of any instrument, say, of 
 a rod when swung from one of its ends, may be roughly 
 found as follows. Suspend it from either of its ex- 
 tremities by a string, so that it hangs vertically. If 
 it be now struck with a stick at, or near, its top, the 
 lower end will jerk towards the quarter whence the 
 blow comes. If it be struck at or in the vicinity of 
 its bottom, the top, in its turn, will, as it were, bow 
 towards the source of the stroke. An intermediate 
 point will readily be found by experiment whereat a 
 blow will tend to drive the whole rod, including both 
 its ends, altogether and unequivocally in the direction 
 of the force applied. That point is the centre of per- 
 cussion of the rod under existing circumstances. 
 
CHAPTER XII. 
 
 HE reference which has been made to a hoop- 
 stick naturally brings to mind the other 
 member of the partnership to which it 
 belongs, to wit, the hoop. Some of the 
 riddles which a hoop, with all its delusive appearance 
 of extreme simplicity of behaviour, as well as of per- 
 son, offers for solution cannot be expounded without 
 the aid of clues which only a good mathematician would 
 be competent to follow. A few moments' attention, 
 however, may be bestowed on the main feature of its 
 whole duty and conduct in its simplest form, namely 
 that of rolling. The exact method by which this is pro- 
 duced will be best understood if we revert in the first 
 instance to a top, and point out with some particularity 
 of detail how entirely the agencies which are concerned 
 with its spinning differ from those to which the revolv- 
 ing of a top is due. To revert to a top would seem to 
 imply that an omission had been made when that toy 
 was under review, but the one particular point of the 
 manner in which its spinning is generated was advisedly 
 reserved till this moment. 
 
 A top, as everybody knows, is most commonly set 
 
278 
 
 chjldeen's toys. 
 
 going by means of a string which is wound round its 
 spindle, and then pulled. Many other means may be, 
 and often are, employed for the same purpose. Whip- 
 ping tops are lashed; Japanese tops are mostly spun, 
 like teetotums, by the fingers or by the palms of 
 the operator's hands, while peg tops have the por- 
 tions of their persons which are below their waists 
 swathed by a coil of string. It will suffice, however, 
 to consider the single case of a top spun by the employ- 
 ment of a string, as ordinarily done, not only because 
 this is the most typical method, but because this may 
 be taken and treated as being virtually the same as 
 all and each of the plans, whatever they may be, which 
 are adopted in other instances. For the same reason- 
 ing which will disclose the effect of the action of the 
 string will be appropriate, with such slight modification, 
 only, as may be called for by a difference in the form 
 of the tackle used in any given case, to all the means 
 by which tops are spun, every sort of appliance for this 
 purpose, whatever it may be, doing its work on the 
 same mechanical principle. 
 
 Suppose the string to be coiled round the spindle 
 of the top, and thus to be ready for action. I do not 
 know whether spindle or axle is the more proper term, 
 but as we used axle just now we may take spindle for a 
 change. When the operator pulls, he, in fact, as a little 
 consideration will show, virtually produces action on the 
 arm of a lever, one extremity of which is at the axis of 
 the top, and the other, that, namely, to which force is 
 applied, at the point where the free portion of the string 
 meets the surface of the spindle. 
 
 In estimating the mechanical conditions of the state 
 
children's toys. 
 
 279 
 
 of affairs which is thus constituted, attention may, of 
 course, be confined to the field of action of the string, 
 disregarding all the rest of the top, which is merely set 
 in motion through its union with the particular part 
 round which the coil is wound. Since, therefore, all 
 the body of the top which is not directly operated 
 on by the string may be left out of account as com- 
 pletely as if it had been cut away, it may, without 
 introducing any source of error, be conceived to be 
 actually removed. There will then be left for examin- 
 ation a section of the spindle as broad as, but no 
 broader than, the coil of string. This may be again 
 still further reduced, as far as the purposes of the 
 problem which is before us are concerned, by discard- 
 ing all but a mere bar joining the point of meeting 
 of the string and spindle with the centre of the latter. 
 This bar is to be supposed to be rigidly stiff, as is in 
 fact mechanically true of it, so that, although infinitely 
 slender, it will not bend. A pull from the string, which, 
 as will be seen, cannot be given otherwise than virtu- 
 ally at right angles to the bar, twists the latter a little 
 round the centre of the spindle, which is thus an axis 
 of revolution. A very small and momentary compliance 
 with the leading of the string terminates the whole 
 relation between the bar and the external force. The 
 string, uncoiling as it does, and coming off the disc along 
 a straight line, immediately parts companyvwith the end 
 of the bar, since the latter obviously cannot move other- 
 wise than in a circle, after a movement of revolution 
 has been once set up. But the bar, being stiff, has acted 
 as the handle of a windlass would do if similarly moved, 
 turning the spindle of which it is a part a little round. 
 
280 
 
 children's toys. 
 
 Now imagine a series of bars all, respectively, at- 
 tached by one of their extremities to a common centre, 
 and spreading thence outwards, like rays from a source 
 of light, over a circular surface, thus forming a wheel. 
 And suppose an arrangement to be contrived by which 
 a string will exercise a continuing pull at oue particular 
 point of the outside rim of this circular area, then the 
 end of each bar in turn, as the wheel revolves, will be 
 subjected to the action of this force at the spot in ques- 
 tion. If the bars were so numerous and closely packed 
 as actually to touch, they would form a disc, which is 
 what in fact we have to deal with, and the contrivance 
 for making the pull of the string a continuous one is 
 also present in the coil. The spinning of a top is thus 
 seen to be caused by means of a sustained action upon 
 the ends of innumerable bars which are, practically 
 speaking, levers, and which are worked in rapid succes- 
 sion. The whole influence of this action is exclusively 
 confined to turning the levers round, and it has no 
 tendency whatever to transfer the disc which they may 
 be viewed as composing to any other than its actual 
 situation. The axis of the disc thus remains in one 
 fixed position. 
 
 In a hoop, the movement of revolution is produced 
 by mechanical conditions of quite a different kind. 
 Suppose the hoop to be standing stock still, but ready 
 for a start, and therefore maintained in an upright pos- 
 ture by the hand of its proprietor. When it is to be 
 set going, it receives a blow, which, as will be remem- 
 bered, will be delivered to the best advantage if it 
 comes from the centre of percussion of the hoop- stick. 
 If the hoop were floating freely in air or water, so as 
 
children's tots. 281 
 
 to be wholly surrendered to the full effect of any pro- 
 pulsion which, it might receive, without distortion of 
 the result by the intervention of any fresh agent, the 
 point at which a blow would have to be administered, 
 to produce the greatest degree of movement of trans- 
 lation which its force could generate, would be readily 
 ascertained. For, from what has been said, it is clear 
 that it would be situated in the straight line represent- 
 ing the direction of the impulse, and passing through 
 the centre of gravity of the hoop. Now, the course of 
 the hoop, since it must take place along the surface of 
 the ground, which we will assume to be flat, will be of 
 necessity horizontal. 
 
 Suppose, then, a blow to be given, whose direction 
 is horizontal and such as would also pass through 
 the centre of gravity, of the hoop, i. e. through the 
 centre of the circle formed by the rim. The point 
 of impact of a blow thus aimed will obviously be just 
 half way up the rear side of the hoop. The tend- 
 ency of a blow like this is simply to convey the whole 
 hoop, bodily, in its existing attitude, but without 
 any movement of revolution, along the straight line 
 in which the impulse which has been generated acts. 
 But directly the hoop begins to move, another force 
 comes into play, namely, that of friction, which is gen- 
 erated by the rub against the ground of the particular 
 portion of the rolling ring which is, for the moment, 
 in contact with it. The action of friction must, from 
 its nature, always take place in a direction exactly op- 
 posite to that of the motion of which it is the conse- 
 quence. It is, in fact, reaction, which, as you already 
 know, is always exactly contrary to action. Thus its 
 
282 
 
 children's toys. 
 
 effect in the instance which is before us is to resist the 
 passage of the lowest portion, for the time being, of the 
 hoop along the surface of the ground. Were the 
 motion of the upper part of the hoop similarly opposed, 
 and to an equal degree, no propensity to revolution 
 would arise, but since the upper surface is free to follow 
 the impulse by which it has been animated, its pro- 
 gressive tendency, as will readily be seen, is such as to 
 turn it over the retarded point of the circumference of 
 the hoop as though round a fixed axis. The two sides 
 are manifestly neutral in the adjustment of the balance 
 of the forces by which rotation is determined, so that 
 the hoop may be considered as wholly surrendered to 
 the control of the pair of agencies which have been 
 noticed, and the natural consequence must be such as 
 has been pointed out. One distinction which there is 
 between the spinning of a top and that of a hoop has 
 now become plain, and it is this, namely, that in the 
 former case the axis of revolution is stationary, and 
 that in the latter it has a progressive motion. 
 
 A sentence or two at this place on the subject of 
 friction may not be ill bestowed, since it is a force 
 which, as we surmise, pervades Creation generally, toys 
 and the rest of the Universe included, and we have 
 continually had occasion to refer to it. It causes, as 
 we know, the rolling, and is active in the stopping, of 
 every child's hoop that is ever trundled, but it concerns 
 itself with larger matters, since it strives to arrest 
 the progress of whatever moves, if rubbing against 
 anything on the road is an incident to the process of 
 accomplishing a change of place. Water, for example, 
 running through a pipe, moves more slowly at the 
 
children's toys. 
 
 283 
 
 outside than at the middle of the current, owing to the 
 friction of the liquid against the interior surface of the 
 channel. 
 
 The theory is largely entertained, although not 
 universally accepted, that the expanse of the Heavens 
 is filled with ether of extreme tenuity, so that friction 
 acquires some power of acting on all the bodies which 
 traverse space, since they have to part this thin vapour 
 or medium,, or whatever it may be called, in their 
 flight. The fact which has been noticed, and well 
 verified, that certain comets do not reappear so soon as 
 they should, and would do, were not their proper speed, 
 as calculated in their known orbits, retarded by some 
 agency or other, is, rightly or wrongly, taken as evi- 
 dence, no other explanation of this anomaly in their 
 conduct being at present forthcoming, that they have 
 to cleave an attenuated atmosphere of some kind or 
 other. This Ether, as is surmised, by the coherence of 
 its particles, or by their inertia, that is to say, by their 
 indisposition to be jostled aside, causes friction, where- 
 by a sensible reduction of the comet's speed is brought 
 about. If this be really so, the Earth, although it 
 is not, like a comet, a mere glittering film of silvery 
 haze, yet it must none the less, in the fulness of time, 
 when its speed of revolution in its orbit, and the con- 
 sequent centrifugal force, have both together been 
 gradually undermined by friction, be carried into the 
 Sun. For the attraction of gravity which will have 
 been less and less kept in check, will then be absolute 
 master of the situation. At this goal of our course we 
 shall have been preceded, no doubt, by many comets, 
 which, like moths flitting in lessening circles round a 
 
284 
 
 children's toys. 
 
 flame, and eventually immolating themselves in it, will 
 have already hurried to destruction. 
 
 Friction has been spoken of as the direct opponent 
 to motion. In some respects it is so, but notwithstand- 
 ing that general tendency, it is in many cases indispens- 
 able to the accomplishment of progress. In the instance 
 of railway carriages travelling along smooth rails there 
 is much less friction than is excited by vehicles on an 
 ordinary road, the diminution of the force which is an- 
 tagonistic to progress having been the very reason for 
 the adoption of the metals. Consequently, a train is 
 far more readily drawn on rails than it would be on a 
 highway. But the train cannot be started or kept 
 going without the aid of friction, for it is this alone 
 which causes the driving-wheel of the engine to bite 
 the metal and thus itself roll forwards, dragging the 
 carriages after it. Were friction absent, this wheel 
 would spin fruitlessly in one spot, as, indeed, we often 
 see it do for a moment or so at the starting of a very 
 heavy train when its power to grip is overborne by 
 the strain caused by the inertia of the load which is 
 to be moved. 
 
 Similarly, in the case of a cart and horse, friction 
 is an indispensable condition of progress. Smooth- 
 ness of the road means, no doubt, a mitigation of the 
 resistance which the horse has to overcome in draw- 
 ing the vehicle. But it also means a diminution of 
 the friction between his shoes and the surface of the 
 road, that is to say in other words an impairment of 
 the effectiveness of his foothold. Therefore, when 
 friction is reduced to a disadvantageous extent, as in the 
 case of a road coated with ice, progress becomes pro- 
 
children's toys. 
 
 285 
 
 portionately difficult to accomplish. It is friction which 
 enables us to walk, and it need scarcely be added that a 
 walking-stick would be useless in the absence of this 
 force, since its lower end, slipping unrestrainedly as it 
 would then do, could acquire no fixed point of support 
 on the ground. Propulsion therefore would not be 
 obtainable, since there would be no resistance against 
 which to thrust, nor, without friction, could the other 
 end of the stick be retained in the grasp of the pe- 
 destrian. 
 
 The force of which we have been speaking is not, 
 like gravitation, a mysterious power of which we can 
 give no further account than that it exists, and that 
 its operation may be watched and measured. It is 
 simply cohesion resisting motion, and is not, there- 
 fore, strictly speaking, a force at all. It has no tend- 
 ency to generate motion, which is the main essential 
 characteristic of a force. Its nature may be described 
 as follows. Suppose that you have a very smooth sur- 
 face such as that of a looking-glass, or an even yet 
 more sleek-faced object, such as one of the Whitworth 
 planes which were alluded to just now, however care- 
 fully it may have been polished down towards a con- 
 dition of extreme flatness, there still always must and 
 will occur in it tiny prominences and depressions ; in 
 fact it will be a hilly plain, and will stand revealed as 
 such when closely examined under a microscope. Now 
 suppose another surface of a like character to be made 
 to slide over this. This second surface, however level 
 to the eye, will, in reality, be similarly rugged, and 
 consequently, when the two are in contact, and when 
 there is motion either on the part of one only, or on 
 
286 
 
 childben's toys. 
 
 the part of both, but not precisely at the same rate, 
 and in the same direction, there must ensue a process 
 of bumping of the tiny mountains which emboss the 
 one against those which pimple the other, as progress 
 is made. Rub the faces of two nutmeg-graters to- 
 gether, and you will get a clear-cut illustration of 
 what is meant. 
 
 Friction augments with any increase of the force 
 which presses together two moving surfaces, because 
 then the little asperities which have been spoken of, 
 instead of sliding over one another with more or less 
 difficulty, are forcibly brought to succumb to a violent 
 process of mutual grinding, by means of which they are 
 partially or completely levelled. The cohesion of their 
 particles does, of course, its utmost to resist this de- 
 molition of their structure. 
 
 For the purpose of conveying a general notion of 
 friction as a whole, it has been spoken of, advisedly, up 
 to this point, as if it were a force whose origin and 
 manifestations are always uniform. But this would be 
 an inaccurate account, if it were to be put forward as 
 altogether true in detail. Friction is of two kinds. 
 One of these occurs in the case where it successfully 
 resists the occurrence of any motion whatever. Take, 
 for example, any object standing upon any table. No 
 table or any other surface is (or at least the chances 
 against its being so are infinitely great) exactly hori- 
 zontal. If, therefore, it were absolutely smooth, and 
 anything standing upon it were so also, the latter 
 would of necessity certainly behave like a ball placed 
 upon an inclined plane, and slide downwards towards 
 the lowest situation which it could reach. Things 
 
children's toys. 
 
 287 
 
 placed upon a table remain stationary in consequence 
 of friction : that is to say, the roughness of the sur- 
 faces which are in contact quells all impulses towards 
 motion before they can generate any effect whatever. 
 The tiny eminences are, as it were, interlocked. Now 
 when friction thus maintains rest it is usually called 
 in the language of mechanics " statical friction." If 
 by the application of some external force, as, for ex- 
 ample, by a push, you cause the object which has been 
 hitherto stationary to travel along the surface of the 
 table, friction, or rubbing, of another, and more active 
 kind, is called into being which is termed " dynamical." 
 It is self-evident that an account might be given of 
 dynamical friction by saying that it represents the 
 transference, or transformation, of some part, more or 
 less as the case may be, according to circumstances, of 
 the motion of a moving body. It is either shifted over 
 to the particles of the medium, or surface, which en- 
 virons or touches the line of march, producing among 
 them a certain amount of dislocation of arrangement, 
 or, if displacement be more or less successfully resisted 
 by them, then motion to the same amount reappears 
 as its alter ego — that is to say in its other phase of 
 heat. The conditions on which the powers of statical 
 and dynamical friction respectively depend are not 
 quite the same. This matter is one which is recom- 
 mended to you for consideration hereafter. 
 
 It will be now seen why no general rule, applicable 
 to all circumstances alike, can be laid down by which 
 the precise spot at which a hoop should be struck in 
 order to produce the fullest effect of impulsion will be 
 ascertainable. If the path along which the hoop is to 
 
288 
 
 children's toys. 
 
 travel be very rough, that is to say if the obstacles 
 with which it is beset be high and stiff, friction will be 
 diminished if the blow from the stick be delivered low, 
 so as to have, as it were, something of a lifting tend- 
 ency, which will ease the transit of the projections 
 over one another, and thus avoid evoking the obstinacy 
 which would attend a more direct and uncompromising 
 conflict. If, on the other hand, the course which is to 
 be travelled be smooth, the higher will be the point 
 which will be struck to the best advantage, provided, 
 of course, that it be never above the horizontal line 
 passing through the hoop's centre of gravity. For sim- 
 plicity's sake, as you will remember, the hoop is sup- 
 posed to journey on a flat path. The proper adjustment 
 of traces with a view to economy of power in draught 
 by horses will, of course, be prescribed by considerations 
 some of which depend on friction. 
 
CONCLUSION. 
 
 The time which we have now spent among toys, 
 although it has been long enough, perhaps, to exhaust 
 your patience, has yet been insufficient for the complete 
 discussion of any one of the subjects which have come 
 under review. Supposing, therefore, as seems to be the 
 case, that we have now glanced at most of the common 
 playthings which first come to hand in an ordinary 
 nursery or playroom, there is no occasion to beat fur- 
 ther afield, so as to take in others whose claim to be 
 regarded as toys is debateable, since any inexhausted 
 capacity for attention with which you may be credited 
 would be better employed in surveying once more the 
 ground which we have traversed too hurriedly, rather 
 than in prosecuting expeditions into fresh territory 
 which we are not strictly called upon by the terms of 
 our programme for this evening to explore. Otherwise, 
 a tobacco pipe, whenever it is used for its best, al- 
 though not its primary purpose, namely, that of blow- 
 ing soap-bubbles, might be held to have a just title to 
 take rank as a toy. Blowing bubbles may claim to bear 
 some semblance of an historical, as well as other, interest. 
 For it may be supposed that the idea of a balloon is due 
 
 u 
 
290 
 
 children's toys. 
 
 to the suggestion offered by Nature through bubbles. 
 Indeed, the first rudimentary project of lifting some 
 kind of bag into the upper air by means of inflation with 
 a fluid lighter than the atmosphere, took the form of 
 blowing soap-bubbles full of gas. But to do our duty 
 properly by a soap-bubble would take an indefinite 
 quantity of time and pains. For it presents illustrations 
 of the working of many of the laws of Nature which are 
 of the widest application, of the most paramount im- 
 portance in the arrangement of the Universe, and the 
 main sources of order and beauty. 
 
 For example, on sitting down with a pipe and a basin 
 of soapsuds preparatory to commencing operations in 
 bubble-blowing, it would be impossible to help noticing 
 that most, but not quite all, of the separate little cham- 
 bers of which any mass of the foam which is before us 
 is composed are hexagonal, that is to say, six-sided. 
 There must be some cause for this. On learning how 
 this arrangement is brought about, the reflection must 
 immediately occur that the agency to which it is due 
 must be at work all over the domains of Nature. Such 
 is discovered to be the case, since its characteristic 
 mark will be detected scored upon innumerable animal, 
 vegetable, and mineral structures. On proceeding to 
 blow bubbles, it is found that for some reason or other, 
 although they may be elongated for a moment by a stiff 
 blast into a grape-like form, they cannot be made to 
 retain permanently, or even for a moment, with their 
 own consent, any other shape than that of around ball. 
 An acquaintance with the law to which the bubbles so 
 obediently and persistently conform reveals to us the 
 origin of the figures of numberless things in nature, 
 
children's toys. 
 
 291 
 
 among which is that of the globe on which we live. The 
 same law is at the bottom of most of the mechanical 
 work which is done in the world, whether it be such as 
 Nature herself undertakes, or that which the hand of 
 man accomplishes by the intervention of machines. 
 
 The lovely iridescent hues which adorn a bubble 
 cannot fail to excite a curiosity which is not very easily 
 gratified, since the department of the science of optics 
 which treats of the origin of what are called " the colours 
 of thin plates " is rather a difficult region of study. 
 The coat of many colours which forms both the body and 
 raiment of a bubble is of a finer texture than was ever 
 turned out from the fairies' loom, since, according to Sir 
 Isaac Newton who measured it, and who had a trick of 
 being right, it is at its thinnest part not more than 2 ^ m 
 of an inch thick. I mention these facts merely, if pos- 
 sible, to excite interest and stimulate inquiry by show- 
 ing that as there are, as we know, u sermons in stones," 
 so, also, there are teachings in toys which are worth 
 eliciting. 
 
 The road to an elementary knowledge of common 
 things may seem a little harsh at the outset to the 
 unpractised tread, but those who find this to be so may 
 take heart of grace through the confident assurance that 
 the path will soon become one of pleasantness. On the 
 wall of a dungeon in the Tower there is an inscription, 
 carved, as its tone and import would seem to indicate, 
 by some poor doomed prisoner, condemned to death, 
 and equipping himself with calmness for his last journey. 
 It runs thus : " Par passage penible passons a fort 
 plaisant." The seriousness, if not pathos, which these 
 few words seem to condense impressed me, when I first 
 
292 
 
 children's toys. 
 
 read them, on being taken, as a boy, to see the Tower. 
 They apply with truthful and grave force to such efforts 
 as any of us can muster the courage and spirit to make 
 for our own improvement. 
 
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6 
 
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12 
 
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14 
 
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 15 
 
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