GIFT OF NOMOS. NOMOS. LONDON : Printed by SPOTTISWOODE & Co. New-street-Square. NOMOS : ' AN ATTEMPT TO DEMONSTRATE A CENTEAL PHYSICAL LAW IN NATURE. How hardly in the midst of our hurry, and jostled by the cares of life, Shall a man turn and stop to consider mighty secrets ; With barely hours, and barely powers, to fill up daily duties, How small the glimpse of knowledge his wondering eye can catch." PROVERBIAL PHILOSOPHY. LONDON: LONGMAN, BROWN, GREEN, AND LONGMANS. 1856, 73 CONTENTS. PAGE INTKODUCTION 1 CHAPTER I. SEAECH AFTEB A CENTEAL LAW IN THE PHENOMENA OP AETIFI- CIAL FOECE. The connexion between artificial electricity, magnetism, light, heat, chemical action, and motion, not separable ... 8 This connexion indicates a concealed central law ... 8 Search after this central law in the phenomena of electricity . 9 Identity of the different kinds of electricity .... 9 Identity of voltaic and ordinary electricity .... 9 Apparent difference a difference of quantity, and not of kind . 16 A 3 248203 11 CONTENTS. PAGE Identity of voltaic and ordinary electricity with the other kinds of electricity .19 The analogies of the states called "conduction" and "insula- tion," "charge" and "discharge," "current" and "tension" 20 The connexion between chemical and electrical action . . 27 This connexion in the fluid parts of the circuit . . .29 This connexion in the metallic parts of the circuit . . .31 This connexion in the aerial parts of the circuit . . .33 The current a chemical idea 35 The forces concerned in the current are not of greater intensity than chemical forces 45 The laws of chemical affinity are never suspended in the cur- rent 49 The transfer of matter in the current to be referred to chemical changes 51 The reason why chemical forces are intensified in the current . 54 Elucidation of the phenomenon called " tension" . . .55 Electrical attractions and repulsions (?) to be referred to chemi- cal changes . . . .56 The existence of true repulsion questionable . . . .59 The connexion between electricity and magnetism . . .61 The rotation of a magnet around an electrical conductor . . 65 The rotation of an electrical conductor around a magnet . . 66 CONTENTS. VU PAGE The explanation of this rotation . . . . . .68 The rotation of an electrical conductor around an electrical conductor 77 A magnetic needle must arrange itself across an electrical con- ductor 81 The magnetic needle must point to the poles of the earth . 82 No special electrical currents in a magnet . . . ,83 " Magnetism" a mere mode of electrical action . . .83 The bearing of these considerations upon the theory of elec- tricity '.. ; . . . . * 'i*- "- . . 83 As showing the presence of chemical changes in a metallic con- ductor during the passage of a current . . .83 As explaining the reason why the loadstone and steel retain their "magnetic" power . . . . . . . 84 Electrical light must be referred to chemical action . . 86 Electrical heat must be referred to chemical action . . .88 The expansive effects of heat to be explained on the same hypothesis 89 The whole history of electricity points to a central law which for convenience may be termed provisionally the law of the laboratory . . . 92 Character of this law of the laboratory 92 Eeasons for supposing that this law has a wider scope than the laboratory . . .93 A 4 Vlll CONTENTS, CHAP. II. SEAECH APTEB A CENTBAL LAW IN SOME OF THE PHENOMENA OF NATUEA1 MOTION. PAGE The laws of Kepler 94 Newton's interpretation of these laws 95 The Newtonian philosophy of the heavens . . . .95 Some difficulties which are not altogether explained by this philosophy 105 The probability that space is not the incorporeal void which is necessary to allow the unimpeded operation of projection . 105 Application of the law of the laboratory to the explanation of the translatory movements of the earth . , . . 108 This law will account for the eccentricity of the orbit . . Ill This law will account for the rotation upon the axis . . 113 Difficulty of applying this law to the explanation of the move- ments of the companion planets . "-;.. 113 How this difficulty may be overcome . . . . . 114 How the particular orbital eccentricities of the planets are to be accounted for ... . . . , . v . 115 All the planets must rotate upon their axes . .- ; . . 118 The taw of the laboratory will account for the movements of comets, and explain their peculiarity . . . . . . 119 CONTENTS. IX PAGE The law of the laboratory will account for the movements of the satellites .* ''.' ' i, . >'' V- ; 122 The law of the laboratory will account for the movements of the sun . , " . -. "'.- 122 The " attraction of currents " is the real force of gravity "T.. 123 Hence, the movements of the heavenly bodies are due, one and all, to the law of the laboratory . . . ... t , . . 124 CHAP. III. SEAECH AFTEB A CENTEAL LAW IN SOME OP THE PHENOMENA OF NATUEAL HEAT. The importance of heat in the economy of nature . . , 125 The amount of solar heat communicated to the earth . . 126 Probable effects of this heat . 126 This heat will cause the earth to expand on the side next the sun . 129 This heat will be brought to a focus within the earth . . 131 The objections to this view may be set aside . . . .132 The heat may travel through the earth with extreme rapidity . 134 This focal concentration of heat will cause fusion and expan- sion of the parts corresponding to the focus . . . 136 X CONTENTS. PAGE The effect of this fusion and expansion will cause a permanent bulging out in the equatorial region, and a transient bulg- ing out in the region most removed from the sun . . 136 The moveable bulging out on the side nearest to the sun and on the side farthest away from the sun will be equal, or nearly equal, to each other 137 The tides support the idea that the solar heat acts upon the earth in this manner 138 The present theory of the tides is very unsatisfactory . 139 One great objection to this theory 139 Another great objection to this theory . . . . . 140 A third great objection to this theory 140 Another theory of the tides which obviates these objections . 143 In this theory the lands immediately under the sun and the lands directly away from the sun are supposed to rise out of the waters in obedience to that expansive action of the solar heat which has been explained, the water retaining its level . 143 In this action the moon will act in the same manner as the sun, and with greater power 146 The metamorphosis of comets supports the idea that the solar heat may have this peculiar expansive action . . . 148 The volume and rarity of comets 149 The changes in Halley's comet in 1835 151 The solar heat may cause the ejection of nebulous matter from the side nearest the sun . . . . . . 153 CONTENTS. XI PAGE The solar heat may be concentrated at a focus in the interior, and the focus may be the luminous nucleus . . . . 153 This focus may undergo the changes which the nucleus is seen to undergo .......... 155 The effect of this focal action may be to expand the overlying substance of the comet into the tail 155 The remaining metamorphoses may be accounted for in the same manner 156 The past history of the earth furnishes other and very marked illustrations of the idea that the solar heat may exert this peculiar expansive action . . . . . . . 159 The original condition of the earth, according to the Scrip- tures, was that of a shoreless ocean ... . 160 The land may have been raised out of the waters, and its foundations fixed, by the expansive action of solar heat . 162 By the same action the land may have been submerged and again raised in another place, as occurred at the deluge, if the position of the earth in relation to the sun had been changed 163 The details of the deluge support the idea that the land was raised in this manner . 166 The repeated revolutions of the preadamite world form an ob- jection to this view, for, once raised, there could be no change in the relative positions of land and sea without a miraculous change in the relative positions of the sun and earth . . 169 Xll CONTENTS. PAGE The idea of repeated revolutions not unscriptural . . . 170 The preadamite cosmogony 171 Dr. Young's opinions 175 The "fire-mist theory" and the "chemical theory" not neces- sary to account for the internal heat of the earth . . 175 The internal heat of the earth a necessary consequence of the manner in which the sun acts upon the earth . . . 176 The original condition of the earth may be that which is de- scribed in Genesis 177 The earth need not be of extreme antiquity .... 177 The coal-strata, as a rule, may have been formed within a com- paratively limited period, because they are formed from drifts^ and not from forests growing on the spot . . . 178 The limestone-strata, as a rule, may have been formed within a comparatively limited period, because they are formed from drifts^ and not by animals living on the spot . . . 181 The other stratified rocks, as a rule, are certainly the product ot drifts 183 These strata may therefore have been formed in one epoch, for if the coal-strata and limestone-strata are the product of drifts, the one may have drifted upon the other in the same basin, and there is no necessity that each stratum should represent what was once a living and growing surface of the earth . . ' . . 183 CONTENTS. Xlll PAGE Evidence that these strata were formed in one epoch . . 184 Th6 organic remains entombed in the strata show that the process of stratification must have been rapid, for, if other- wise, these remains must have been removed by decay . . 185 Evidence, apart from these remains, that the stratification may have been rapid 186 In Dr. Young's opinion the few months of the deluge would allow sufficient time for stratification 188 The opinion of Woodward, that the period of stratification extended from the creation to the deluge, more probably correct . v . * . * - " .. . . 188 No evidence that stratification began before the Adamic epoch 189 Hence, geology appears to speak only of that mighty revolution which destroyed the antediluvian world . . . . 189 Hence, geology affords no objection to the idea that the land must remain in the same position so long as the earth retains its present relation to the sun 189 Hence the deductions of science harmonise with and explain the statements of Scripture, and the deductions and state- ments are in perfect keeping with the facts of geology . . 189 Natural heat may be referred to the law which we named pro- visionally the law of the laboratory . . . . 190 The law of the laboratory affords the only explanation of na- tural heat . .... 190 XIV CONTENTS. PAGE Natural heat may be taken as another argument that the law of the laboratory is the law of nature 190 A possible reason why there is evident heat in the rays of the sun and none in the rays of the moon 191 CHAP. IV. SEARCH AFTER A CENTRAL LAW IN THE PHENOMENA OF NATURAL LIGHT. Natural light may be referred to the law which we named pro- visionally the law of the laboratory . ... 192 The law of the laboratory affords the only explanation of natural light . 193 Natural light may be taken as another argument that the law of the laboratory is the law of nature . . . 193 The Scriptural account of the creation appears to show that light and motion are bound up in a common cause as they are in the law of the laboratory 193 A collateral inference that the creation of the earth was not long antecedent to the creation of Adam *. . . . , . 193 CONTENTS. XV CHAP. V. SEAECH AFTER A CENTRAL LAW IN NATURAL CHEMICAL ACTIONS. PAGE These chemical actions may be referred to the law which was named provisionally the law of the laboratory . . .195 The law of the laboratory affords the only explanation of these actions 195 These actions may be taken as another argument that the law of the laboratory is the law of nature . . . T "-. . 195 CHAP. VI. SEAECH AFTER A CENTRAL LAW IN NATURAL MAGNETISM AND ELECTRICITY. The phenomena of natural magnetism and electricity may be referred to the law of the laboratory .... 196 The law of the laboratory affords the only explanation of these phenomena . . . 196 These phenomena may be taken as other arguments that the law of the laboratory is the law of nature .... 196 CONCLUSION . . 197 N it Si AN ATTEMPT TO DEMONSTRATE A CENTRAL PHYSICAL LAW IN NATURE. IT needs not the gift of prophecy to perceive that many changes in philosophy must result from that mighty revolution in society which is now in pro- gress. The philosopher no longer lounges in his chair and dreams away his time in happy confidence in his own opinions, but he has been roused by the events which have startled the monarch on the throne and the priest at the altar, and he now doubts where once he dogmatised. He doubts, and he does not yet divine what the end of his doubts will be. Now the creed of science is questioned in nothing more than in the articles which relate to the philo- sophy of the laboratory, and in these articles a change is necessary which is great in itself, but greater still in its results. It is no longer possible to believe implicitly in the different agents which have played so prominent a part in this philosophy. What is electricity ? It is no single agent : it is a name for many agents in one heat, light, magnetism, and others. What is magnetism ? Nothing apart from electricity. What is artificial light? Like natural light, it goes hand in hand with heat, and it has the same power of working chemical wonders upon the magic screen of the photographic camera. What is heat? It is one of the signs of luminous, and electri- cal, and chemical action. What is chemical power ? A power which bursts into light and heat in flame, and which changes into electricity and magnetism in the galvanic trough. What are the attractive forces which are associated with electricity and magnetism, and which play so important a part in chemical changes ? Nothing is known about them, and, after all, they may prove to be only varying aspects of that force of attraction which is supposed to be neither electrical, nor magnetical, nor chemical, even the force of gravity. Indeed, so intimate and inseparable is the connexion between these agents, that it is more easy to look upon them as signs of action than as agents. Nor is this the only change which is necessitated in this part of the creed of science. It is commonly held that electricity and the companion phenomena are not only agents, but imponderable agents, agents, that is to say, which are quite beyond the scope of physical inquiry. This opinion, However, is as groundless as the other ; for, on careful inquiry, these so-called agents appear to be signs of a certain NOMOS. 3 lefinite action in ordinary matter, an action which is found to be obedient to the ordinary laws of che- mistry. The inquiries which have led to these conclusions have also led to the discovery of certain movements, which are themselves of great importance, and which furnish the interpretation to other movements of greater importance still. It is evident, in short, that the most fundamental changes are necessary in these subjects ; and, so far, the whole burden of evidence appears to point to some general law of which light, heat, electricity, magnetism, chemical power, and some kinds of mo- tion, are only so many effects. So far, the whole burden of evidence appears to point to some central law as underlying these so-called agents. But if great changes are demanded in these mat- ters, great changes are also demanded in other and still more important departments of philosophy. It is not easy, indeed, to draw a distinct line of demar- cation between artificial and natural light ; and it is equally difficult to separate the phenomena which are correlative of artificial light, from the phenomena which are correlative of natural light. Out of the la- boratory, light, heat, electricity, magnetism, chemical power, and certain kinds of motion, appear to be associated in the same manner as in the laboratory. Light, heat, and chemical power attend upon the force of gravity in the solar ray, and render it diffi- cult to regard this force as an isolated and independent agent ; and it is not easy to suppose that magnetism B 2 4 NOMOS. and electricity do not enter into the perfect idea of that law by which the earth is ruled. In a word, there are signs abroad which seem to show that the experience of the laboratory has a far wider scope than was at first apparent. Here, then, is the prospect of other changes in the creed of science ; for if this be so, it is at once apparent that many changes must take place in the mode of interpreting several cosmical phenomena. If the law of the laboratory if we may use this term to express that central law to which the philosophy of the laboratory appears to point be a universal law, it is necessary that space should be filled, not merely with imponderable ether, but with actual matter ; for, according to the law of the laboratory, light, heat, and their companion phenomena are the effects of a definite change in matter ; and if there be ponder- able matter in space, there must be a resistance to the motions of the heavenly bodies which is not sup- posed to exist at present. At first sight, then, it would seem that the law of the laboratory cannot be a universal law. But this is not a necessary con- clusion. Now, unquestionably, the orbital movements of the heavenly bodies may be accounted for by sup- posing that these bodies were set in motion by a tangential impulse in free space, and then left to the action of the force of gravity. The evidence is un- impeachable. But this is not the only explanation. On the contrary, it may be shown that the heavenly bodies must rotate upon their axes and course on- wards in orbits of various eccentricity if they obey NOMOS. 5 the law of the laboratory in a region where they encounter a certain amount of resistance in moving. It may be shown also that these movements must begin as well as continue under these circum- stances. And hence it is not unreasonable to sup- pose that the law of the laboratory may be the law which governs the movements of the heavenly bodies. But be this as it may, it is very certain that the force of gravity is not sufficient of itself to account for every phenomenon in which it is supposed to be the principal or exclusive agent. It does not fully account for the tides, or for the wonderful changes which are exhibited in the form of comets. In order to account for these phenomena, it appears to be ne- cessary to have recourse to another agency an agency which must operate, but whose operation has never yet been properly considered. This is heat. Nay more, it is also found that the same agency which will account for the tides, and for the changes in the forms of comets, will kindle a fire in the heart of the earth, and keep the land above the waters in such a way that in very truth " the bounds of the sea are fixed by a perpetual decree, so that they cannot be passed ; " while at the same time it will do much to elucidate what is dubious in the various versions of the past history of the earth. It is found, indeed, that another power, and one scarcely inferior to that of gravity, must be admitted into the idea of cosmical law ; and as this second power enters into the idea of the law of the laboratory, this very fact " O NOMOS. becomes an argument that the latter law is none other than a partial conception of cosmical law. Nor have we yet arrived at the limit of the in- novations which appear to be required in the creed of science ; for, on pursuing the inquiry, the same law is found to lead us to the physical interpretation of natural light and its associate phenomena. No very satisfactory explanation has yet been offered of natural light. It is, we are told, the sign of an undulation of inconceivable rapidity in an im- ponderable ether which pervades all space. The imagination is taxed to the utmost to take in the subtle conception. But this difficulty is at an end if the law of the laboratory be invoked to the ex- planation of the phenomenon, for then the light becomes the necessary effect of the law. The light reveals the presence of the law, and the law explains the nature of the light. It is so also with natural heat, with the chemical powers of the solar ray, and with the manifold mani- festations of terrestrial electricity ; and it is not too much to say, that we know nothing about their causes, unless we allow the law of the laboratory to be a universal law. If we do this, then they become only so many signs and effects of the law, and the difficulty is, not to account for their presence, but to imagine their absence. The law of the laboratory, then, must be regarded as a cosmical law, for the more it is examined into the more it is seen to gain in comprehensiveness, until at length it loses every trace of speciality. This, NOMOS. then, is the great change which appears to be ne- cessary in the creed of science ; and that this change is necessary, and that it will lead to the results which have been specified, is what we propose to show in the following pages. B4 NOMOS. CHAPTER I. SEARCH AFTER A CENTRAL LAW IN THE PHE- NOMENA OF ARTIFICIAL FORCE. THE researches of late years have shown that the artificial manifestations of electricity, light, heat, and many other agents, are connected in a very intimate manner ; and the question of the present day is, not whether they are thus connected, but ^between" whether we are to agree with Mr. Grove eiectridt * n re g ar ding them as reciprocally trans- light, heat, mutable. Or rather the question is, whe- and other agents indi- ther these so-called agents are agents at eating the . f , . . .*** existence of all, for on further inquiry it is found to some hidden -, 11 .-, central law. be more easy to look upon them as signs of action than as agents. Everything, indeed, seems to point to a connexion which cannot be severed, and which renders it impossible to detect the real law of any one agent without at the same time discovering the real laws of the companion agents ; in other words, everything seems to point to some undiscovered central law of which electricity, light, heat, and the associate phenomena, are only so many effects. Is there, then, such a law ? This is the great question which we here propose for solution, and which we will endeavour to solve by analysing, first of all, the phenomena of electricity. We will do this because in these phenomena we find NOMOS. 9 the way which appears to lead most directly to the desired result. What, then, is electricity ? There are, we answer, several kinds of electricity. There is ordinary elec- tricity, or that which is obtained from the gearch after common machine, from the atmosphere, the hidden . central law and from several other sources ; there is in the phe- , . , .. , i i i -i i nomena of voltaic electricity, or that which is yielded artificial by the common pile or battery ; and be- sides these, which are the principal kinds, there are the electricities which are elicited from magnetism, from heat, and from animals such as the torpedo. All these several kinds, however, are allowed to be essentially one and the same. This is allowed ; but it is necessary for our purpose to state the evidence upon which this identity is established, even though this evidence be long and in some respects tedious. At the same time we may assume the identity of the electricities which are derived from magnetism, from heat, and from animals such as the torpedo, and at once proceed to show the identity of ordinary and voltaic electricity. We may do this because the two latter kinds of electricity are incomparably more im- portant than the others, and because the identity of the others with themselves and with these is proved by a similar train of arguments. We pro- ceed then, first, to consider the identity of ordinary and voltaic electricity a ques- tion of great interest and importance, and one which affords the clue to almost all the questions which remain in the background. 10 NOMOS. In considering this identity, we will take the evo- lution of heat, the magnetism, the chemical action, the shock, and the spark all of which are familiar phenomena of voltaic electricity as preliminary points of comparison, It is well known that ordinary electricity agrees with voltaic electricity in the evolution of heat, and that a wire may be fused by either kind indiffer- ently, provided the quantity be sufficient. Ordinary electricity agrees with voltaic electricity in the power of magnetising iron or steel, and the direction of the magnetic current thus induced holds the same constant relation to the electrical current in either case ; but ordinary electricity has not the same power of deflecting the magnetic needle as voltaic electricity. M. Colladon, of Geneva, how- ever, was led to suppose that this difference might be owing to the use of very insufficient quantities of ordinary electricity ; and, on remedying this de- ficiency, he procured the wanting deflection. Nor need it be any matter of surprise that deflection should be wanting under ordinary circumstances, for the very shock of the discharge is sufficient to de- range, diminish, or even invert, the magnetic power of the needle. And this is the great reason why the deflection was so long wanting, for Dr. Faraday has shown that the needle is deflected even by small quantities of ordinary electricity, if a sufficiently delicate needle be used, and if the shock be dimi- nished and the discharge retarded by causing the current to pass through wet thread or through some other bad conductor. He has also shown that the NOMOS. 1 1 needle moved to this side or that as the direction of the current changed, and always in obedience to the law which rules the movements of the needle under voltaic electricity. Ordinary electricity agrees with voltaic electricity in being attended by the same signs of chemical action. This has been proved by Dr. "Wbllaston, and more conclusively still by Dr. Faraday. The latter philosopher obtained his proof by passing ordinary electricity through small pieces of paper soaked in certain chemical solutions, the current being first bridled by making it pass in some part of its course through a piece of wet thread. When solution of sulphate of soda was used, the acid was evolved at the places where the current entered and the alkali where it left, and this equally in each piece of paper when several pieces were arranged in a row. The experiment is as follows : " Three compound pieces of litmus and turmeric paper were moistened in a solution of sulphate of soda, and arranged on a plate of glass, with platinum wires, as in the figure. The wire m is connected with the Fig. i. prime conductor of the machine, the wire t with the discharging train, and the wires r and s enter into the course of the electrical current by means of the pieces of moistened paper ; they are so bent as to 12 NOMOS. rest each on three points, nrp, nsp, the points r and s being supported by the glass, and the others by the pieces of paper ; the three terminations ppp rest on the litmus, and the other three nnn on the turmeric paper. On working the machine for a short time only, acid was evolved at the poles or terminations ppp by which the electricity entered the solution, and alkali at the other poles nnn, by which the electricity left the solution."* If the direction of the current be reversed in this experiment, the alkali and acid immediately change places. Now in this, and in all experiments intended to elucidate this point, an important source of error must be guarded against. The electricity must be made to pass through the paper, for if it be allowed to pass over it as a spark, some nitric acid is formed by the com- bination of the nitrogen and oxygen of the atmo- sphere ; and this acid will redden the litmus paper, and prevent the appearance of the brown alkaline stain upon the turmeric paper. This was first pointed out by Cavendish. Such, indeed, is the extent to which nitric acid may be formed under these circumstances, that Dr. Faraday was soon able to form touch-paper out of a piece of paper soaked in solution of potass. This potass became converted into nitrate of potass, or saltpetre, by combining with the nitric acid, and thus the paper when dry became touch-paper. It is said that ordinary electricity, like voltaic electricity, has the power of decomposing water; but this is not proved by the experiments which are * " Experimental Researches in Electricity," vol. i. p. 90. NOMOS. 13 usually cited for the purpose. The quantity of ordinary electricity, as will be shown presently, is altogether insufficient to produce any marked results. Gases are certainly evolved from the water, but their quantity is too small to allow us to speculate upon their nature so small that Dr. Faraday " could not obtain at either pole a bubble of gas larger than a small grain of sand," after working a large machine for half an hour. We shall revert to this point again ; but in the meantime sufficient has been said to show that voltaic and ordinary electricity agree in having, though in unequal degrees, the same definite power of chemical decomposition. Ordinary electricity agrees with voltaic electricity in being attended by the same shock when a strong current is passed through the body, and the results are not dissimilar when weaker currents are experi- mented upon. " When," writes Dr. Faraday, " a wet thread is interposed in the course of the current of ordinary electricity from a battery charged by eight or ten revolutions of a machine in good work- ing order, and the discharge is made by platina spatulas through the tongue or gums, the effect upon the tongue and eyes is exactly that of a momentary feeble voltaic current." Ordinary electricity agrees with voltaic electricity in having light as one of the signs of the discharge. The light of ordinary electricity is distinguished by its instantaneousness, and by being accompanied with a sharp explosive noise ; but if the discharge be retarded by passing it through some wet string away from the place where the spark has to pass, the light 14 NOMOS. is less instantaneous, and it is accompanied by little or no noise. It approximates under these circum- stances to the character of a voltaic spark. It is also to be observed that there is no visible difference between the two kinds of spark when they are taken between amalgamated surfaces of metal, at intervals only, and through the same distance of air. It appears, therefore, that ordinary electricity agrees with voltaic electricity in the points which we have taken as preliminary points of comparison, the evolution of heat, the magnetism, the chemical action, the shock, and the spark, and so far their identity may be allowed. But this is not the only evidence in favour of this identity; and thus, on continuing the inquiry, we find that in both cases there are similar attractions and repulsions (?) before the circuit is complete, and that the actual circum- stances of the discharge may be assimilated in a great degree. The familiar attractions and repulsions (?) which are displayed by the common electrometer are very characteristic of common ordinary electricity. They are very marked, even at considerable distances. Now, there are similar attractions and repulsions (?) in the case of voltaic electricity ; and the only difference is, that they are less marked, and that they do not happen at such great distances. They are, however, very unmistakeable. Thus, the gold leaves of the electrometer will diverge when the instrument is placed in connexion with either end of a galvanic battery, or even when brought within half an inch of the end; and they will again collapse if, after NOMOS. 15 having thus diverged, the instrument be carried to the other end. Why there should be any difference, even in degree, will appear presently. In the circumstances of the discharge there appears to be a very great difference between the two elec- tricities. Ordinary electricity, as everybody knows, may be discharged at a considerable distance through the air. It is enough to bring the knuckle within the neighbourhood of the charged conductor to receive the spark and shock. With voltaic electri- city, on the contrary, actual contact is necessary to the discharge ; and it is generally necessary to moisten the hands which grasp the conductor be- fore the shock can be felt. The discharge of ordinary electricity, however, is greatly facilitated under cer- tain circumstances, as by making the current pass through heated air, or through a vacuum ; and Dr. Faraday has also shown that the discharge of voltaic electricity is facilitated under the same circumstances. He has shown that voltaic electricity may be dis- charged at a considerable distance across the ex- hausted receiver of an air-pump, or when the poles and the intervening space are heated by a spirit lamp, and that the discharge was interrupted when air was re-admitted into the receiver, or when the heat was removed. Voltaic electricity may also be discharged at some distance when the poles are first joined for some time and then separated. Under these circumstances the poles and the surrounding air become heated by the current while the poles remain together, and this heat acts like the heat 16 NOMOS. of the spirit lamp after the poles are separated. The explanation is the same. What then? If there is no real difference be- tween ordinary and voltaic electricity in any of these respects, where is the difference, for difference there assuredly is somewhere? Now the only difference which can be found is in simple quantity, and this is astonishingly great. Dr. Faraday's solution of this question, as of every other question which he has undertaken to solve, is most conclusive. In this solution the first toencebe! lf ~ thing to be determined was whether the same absolute quantity of ordinary elec- tricity sent through a galvanometer under quantity, and different circumstances will cause the same not of kind. deflection of the needle. This was found to be the case ; for, on turning the machine a certain number of times, the needle was always deflected to the same point, whether the charge was collected in one Leyden jar or in several, and whatever the re- tarding power of the medium through which the dis- charge was effected. This point being determined, the next step was to compare ordinary and voltaic electricity, quantity by quantity, by means of the deflection of the needle. In this comparison the machine used had two sets of rubbers, and its plate was fifty inches in diameter. The prime conductor consisted of two brass cylinders connected by a third, the whole length being 12 feet, and the entire surface in contact with the air about 1422 square inches. When in good working NOMOS. 17 order, each revolution of the plate gave 10 or 12 sparks from the conductor, each an inch in length ; and sparks of 10 or 14 inches in length could be easily obtained. The electric battery used consisted of 15 jars, each 23 inches in circumference, and each having about 130 square inches of coating. The galvanometer was one of ordinary sensitiveness, having an arbitrary scale, of which each division was equal to about 4. The discharging train was a thick wire, the further extremity of which was connected with the gas and water pipes belonging to the house. The experiment was to charge the battery by thirty turns of the machine, and then, having included a thick wet string about ten inches in length in the circuit, to discharge the battery through the galvanometer, and notice the deflection of the needle. The result was, that the needle immediately became deflected through five and a half divisions of the arbitrary scale. This is the first fact in the comparison. The next thing was to ascertain how much voltaic electricity was required to produce this amount of deflection ; and now the difficulty was to get a vol- taic apparatus of sufficient minuteness. After many trials, however, Dr. Faraday succeeded in finding that the same degree of deflection was caused by two mere wires, one of platinum and the other of zinc, |^ths of an inch in length, T ^th of an inch in diameter, and T %ths of an inch apart, when immersed in four ounces of water acidulated with one drop of ordinary sulphuric acid (a dilution of which the acid could neither be tasted or tested with any distinct- ness) for three seconds. c 18 NOMOS. Taking the power of decomposition as the mea- sure of quantity, Dr. Faraday also found that iodide of potassium was decomposed, and the same amount of iodine set free by this infinitesimal battery in three seconds as by thirty turns of the large machine. Now it is extremely difficult to realize the extent of this amazing difference in quantity. The amount produced by thirty turns of the machine, if passed through the head of a cat, is enough to cause instan- taneous death ; and what then must be the amount produced by an ordinary voltaic battery, if the merest fragments of wire can give out in an instant so great an amount ! Dr. Faraday calculates that the amount produced by the battery in the time required to de- compose a single grain of water, will be at least 800,000 times as much as that produced by thirty turns of the machine an amount which, if measured at all, can only be measured by all the lightnings of a terrific thunderstorm. Although difficult to realize, however, this difference in the quantity of the two electricities is perfectly real, and if other proof is ne- cessary, it may be found in the common Ley den jar. This jar may be charged indifferently by either elec- tricity, and the signs of charge and discharge in either case are perfectly indistinguishable. The only differ- ence is, that the action of charging by the electrical machine is a matter of time and labour, whereas the act of charging by the voltaic battery is the work of an instant. A mere touch with the poles is enough to charge to the utmost. Now this is as we might ex- pect, if, as is certainly the case, a certain quantity is necessary to the charge, and, being so, the jar not NOMOS. 19 only shows the amazing difference in quantity be- tween ordinary and voltaic electricity, but it becomes, as it were, a kind of neutral ground upon which the two electricities are able to meet and display their common properties. With this amazing difference in quantity, then, we need be at no loss to account for any apparent differences in the phenomena of ordinary and voltaic electricity which have not yet been accounted for. We can understand, for instance, how so little water should be decomposed by ordinary electricity, as compared with voltaic electricity, if it requires 800,000 times the quantity which is produced by thirty turns of a large machine to decompose a single grain ; and if the deflection of the magnetic needle bears any proportion to the quantity of electricity acting upon it, it follows that it must be infi- nitely more difficult to cause any deflection by ordinary than by voltaic electricity. These diffi- culties, in fact, cease to be difficulties, and this will appear more distinctly in the sequel ; but we may leave them now, for sufficient has been said to allow us to infer the identity of voltaic and ordinary elec- tricity. The other kinds of electricity are found to possess no characteristic features, and they agree with voltaic and ordinary electricity in every essential identity of particular. All this is proved by a simi- lar train of arguments to that which has just been used ; and as the proof is not at c 2 I 20 NOMOS. all questioned, we will therefore assume that all kinds of electricity are really identical, and proceed once more to ask what is electricity? Before proceeding to put this question, however, it may be well to arrive at some clear conception as to the meaning of some terms in common use, such as conduction and insulation, charge and discharge, current and tension ; for this, we shall find, will ma- terially facilitate our future inquiries. Electrically, bodies are divided into two classes conductors, and non-conductors or insulators; and this division may be illustrated by the The analogies J i-.ii- of the states working of the common electrical machine. called cow- __ ... n auction and The metallic parts are conductors; the insulation, -, 1,1 T charge mA glass parts and the surrounding air are cwr?an