OAK ST HDSF Waril. OF THE UNIVERSITY Of ILLINOIS Return this book on or before the Latest Date stamped below. University of Illinois Library Digitized by the Internet Archive in 2017 with funding from University of Illinois Urbana-Champaign Aiternates https://archive.org/details/microscopeteachi00ward_0 MICROSCOPE TEACHINGS. MICROSCOPE TEACHINGS DESCRIPTIONS OF VARIOUS OBJECTS OF ESPECIAL INTEREST AND BEAUTY ADAPTED FOR MICROSCOPIC OBSERVATION. ILLUSTEATED BY THE AUTHOR’S ORIGINAL DRAWINGS. WITH DIRECTIONS FOR THE ARRANGEMENT OF A MICROSCOPE, AND THE COLLECTION AND MOUNTING OF OBJECTS. BY THE HON. MRS. WARD, AUTHOB OF TELESCOPE TEACHINGS.” LONDON ; GROOMBRIDGB AND SONS, PATBBNOSTEE KOW. 1866. SIS Wz I IT) \ §4 6 PREFACE. "0 i cD C- 0 o Some years ago^ when the beautiful microscope represented in our Frontispiece was a somewhat recent possession of mine^ I took much pleasure in exhibiting its wonders to my friends, at the same time explaining the objects seen. To write an illustrated account of these wonders was a step which followed. The little book, wuth its coloured plates, aided by minute descriptions, was intended as a substitute for the actual exhibition. My object was rather to present these wonders successively to view in the manner of a panorama, than to guide my readers to the practical use of the microscope; for, at the time when I wrote, good microscopes were in the hands only of the few. The case is now altered; excellent instruments, which will answer most purposes, can be purchased for three or four guineas, and the microscope is likely to become, as one of its exponents remarks, ^^the companion of every intelligent family.” Therefore, in again employ- Till PREFACE. ing pen and pencil in the service of the microscope^ my object will be to unite the provinces of the Guide Book and the Panorama; attending to the former, in the hope of making my remarks useful to those who are already in possession of a microscope, while I continue to preserve the latter — namely, the Panoramic method — selecting a few from the multitude of lovely scenes presented by the microscope, in order to attract those readers who, unversed in microscopic marvels, might possibly feel repelled by a complete and length- ened treatise. The utmost care has, however, been taken to make this work strictly accurate in its statements, and exact in its pictorial representations of the objects described. The Author can desire no better success for the book than that its perusal may now and then induce a reader to obtain a microscope, and by its aid enjoy those realities which far surpass all pictures and des- criptions. In the days of my microscopic displays, a working man came, half shyly and half pleased, at the persua- sions of a few of my young friends, to look through the instrument at some striking object. He gazed attentively for a moment, and then exclaimed, in con- siderable surprise, ^Ht is beautiful — but, is it trueT'^ PREFACE. IX ‘‘Yes, my friend,’^ (might have been the reply,) “it is true; it is itself a truth and a reality.” And in this consists the charm of microscopic research. With a suitable instrument, and a little leisure time at com- mand, how happily is the observer brought face to face with the minuter parts of God’s creation, and how easy it seems at once to enjoy and to learn. It is like visiting a rich, but hitherto undiscovered region, — like opening a page, hitherto unread, of a treasured volume. And while we explore and study, we feel a new sense of the unfailing power and infijiite wisdom of the Great Creator, whose mercies are over all His works. Bellair, Moate, Ireland. CONTENTS. PREFACE Page vii. CHAPTER I.— -On Microscopes in general. Points worthy of attention in the choice of a Microscope. Simple Microscopes. Hand magnifier. Coddington lens. Compound micro- ^ scope. Powers of object-glasses. Binocular microscope. Oxyhydrogen and Solar Microscopes. 1 CHAPTER II. — The Microscope unpacked. Explanation of the various pieces of apparatus. Illumination of objects. Lamp. Choice of an object. Opaque and transparent objects. Pre- pared slides. Method for using high powers. Care of the eyes. Shade. Diaphragm plate. Live-box. Care of the microscope. ... 12 CHAPTER III.— Collection and Mounting of Objects. Value of independent research. Special and miscellaneous collections. Collector’s apparatus. The witches’ cauldron. Mounting objects in fluid. Mounting dry and in Canada Balsam. Troublesome air-bubbles. Necessity for method and tidiness 24 CHAPTER IV. — Structure of Insects’ Wings. Few insects without wings. Wing of Earwig. Linear and superficial measures. Wing of Whirligig Beetle. Wings of Wasp. Wings of Dragon-flies. Wing of Trichopteryx atomaria. Evidences of beneficent forethought. 37 CONTENTS. xii CHAPTER V. — Scales of Insects and Fish. Appearance of Butterfly’s wing when divested of scales. Beauty of Butterflies and Moths as opaque objects. Ghost Moth. Green Forester Moth. Burnet Moth. Wings compared to Mosaic. Herald Moth. Emperor Moth. Yellow Underwing. Shaded Scales. Brimstone Butter- fly. Red Admiral Butterfly. Weevils. Singular appearance by trans- mitted light. Scales of Fishes. Eel’s Scale. Polarization of Light. 47 CHAPTER YI. — Hairs and Feathers. Cellular formation of Hairs and Feathers. Cortical and medullary sub- stance. High magnifying power necessary. Hair of White Mouse, Common Mouse, and Rabbit. External layer of Scales. Hair of Otter, Cat, and Bat. Wool, Hair of Horse, Fallow Deer, and Musk- Deer. Human Hair. Hairs of Insects. Down of Birds. Structure of Feathers. Self-acting Hooks of Feathers 65 CHAPTER VII.— Eyes and other Objects. Eye of boiled Fish. Transparent peelings. Eye compared to a camera obscura. Cornea, Iris, and Pupil. Vitreous humour and Crystalline Lens. Optic Nerve and Retina. Fibres of Lens. Teeth of Fibres. Eyes of Insects. Numerous Lenses of Insect’s Eye. Landscapes shewn through Dragon-fly’s Eyes. Internal structure of Insects’ Eyes. Eye of Cricket, Crab, and Lobster. Foot of Spider, Fly, and Boatfly. . 81 CHAPTER VIIL— Vegetable Productions. Valuable information obtained by means of Microscope. Home-made object-glass for exhibiting flowers to children. Characteristic objects from the vegetable kingdom. Rotation of cell-contents. Vallisneria spiralis. Spiral fibre shewn in rind of Collomia. Petal of Geranium. Pollen -grains. Ferns. Discoveries of Count Suminski. The Receipt of Fern-seed. Method of collecting Ferns. Beauty of fresh Ferns. Ex- traordinary number of spores. 103 CONTKNTS. xiii CHAPTER IX.— Organic Remains, Crystals, and Artificial Objfxts. Geological evidence afforded by the Microscope. Fossil Trees. Coal. Fossil Diatoms. Foraminifera from the bed of the Atlantic. Forami- nifera in Limestone Crystals. Method of observing the actual process of crystallization. Microscopic Photographs. Micrometers. Nobert’s Tests. Microscopic Writing 118 CHAPTER X. — The Animalcules and other minute Inhabitants of Water. Animalcules not to be found in Spring Water. Popular fallacy. “Mar- vels of Pond-Life.” Fishing for Frog-spawn. Behaviour of Tadpoles. Picturesque grouping of Animalcules. Inventory of a drop of Pond- water. Infusoria, Rotifera, and Rhizopods. Difficulty of classification. Protococcus and Diatoms. Movements of Xavicula. Diatoms solidified with flint, “Infusorial Earth.” Exquisite sculpture of valves. Heliopelta. 135 CHAPTER XL — The Animalcules, continued. Vorticella. Movements of Cilia. Optical illusion. Stentors. Epistylis. Carchesium. Plants and Animals. Stylonichia. Rotifers. Their Jaws. Four tribes of Rotifer. The Beautiful Floscule. Melicerta ringens. Philodina. Salplna. Water-bear 155 CHAPTER XII — Circulation of the Blood. Young Tadpole’s gills observed. Process of circulation. Arteries. Veins. Tree and River. Capillaries. The journey described in eight stages. Harvey. Circulation in Frog’s Foot observed by Malpighi. Blood corpuscles. Circulation in Reptiles, Fishes, and Crustaceans Method of securing Fish, Tadpole, and Frog. Daphnia pulex. Pale appear- ance of the corpuscles. Minuteness of capillaries. Circulation in young Water-newt. The Heart observed. “Eye of Newt.” Circulation in Bat's Wing. Conclusion 1^8 COLOURED ILLUSTRATIONS. Wings of Earwig. Wasp. Beetles. Wings and Scales of Moths and Butterflies. Scales of Beetles and Fishes. ITair of Mouse. Rabbit. ■ Cat. Otter. Bat. Horse. Deer. Human Hair. Wool. Hairs of Insects. Down of Birds. Structure of a Feather. Structure of the Crystalline Lens. Eyes of Dragon Fly. Cricket. Lobster. FEet of Insects. Petal of Geranium. Pollen of Flowers. Seed Vessels of Ferns. Section of Limestone. Circulation of the Blood in Fish, Frog, Newt, and Bat. TI^Mir' 4 - , '• . V. V. MICEOSCOPE TEACHINGS. CHAPTER L ON MICROSCOPES IN GENERAL. A MICROSCOPE — a complete and beautiful instru- ment by Ross — stands on my table. I have had it so long that it feels almost like a thing indispensable. Yet I recall the time when its purchase was decided on by a kind parent as a desirable help to the researches in which I delighted, and which I had already pursued with a good deal of diligence, aided only by a common magnifying glass. A costly instrument was obtained, worthy too of its high price, from the excellence of its glasses, the extreme finish of all its parts, and the multitude of appliances which accompanied it. It arrived one day from London; its mahogany box was carefully lifted from the packing-case, and the doors were opened. And then I remember feeling somewhat disheartened; firstly by a difficulty B 2 MICROSCOPE TEACHINGS. in finding the uses of all the bright apparatus which met my eye; and next by the want of suitable objects to examine. From various sources information on these points was collected; and to convey it in a simple manner to others is my present object. There is also another kind of information, — of which I was at the outset made personally independent, by the possession of an excellent microscope, chosen, indeed especially bespoken, by an unusually competent judge of such a matter, — but which I have endeavoured to obtain for the sake of others; I mean as to Avhat points are especially worthy of attention in the choice of a microscope, and what luxuries in its apparatus can be dispensed with, with a view to obtain a sufficiently good instrument at a low price. To convey this information, a few words on microscopes in general are desirable. These instru- ments, however various in their details, are made on just two different plans, — the simple and the compound. An explanation of the principle of each will presently be given; meanwhile, it will be sufficient to state that a compound microscope has a long tube, and at least two glasses, one near each end of the tube, while the latter has no tube, and may have only one lens. SIMPLE MICROSCOPES. 3 Reading-glasses, hand-magnifiers, and Coddington lenses, are, in principle, simple microscopes, though that name properly belongs to those only which have a fixed stand : of this class is the smart-looking little instrument which is represented at No. 1, A, No. 1. — A. Simple Microscope. B. Hand -magnifier. screwed on to the lid of the mahogany box, into which it packs nicely when not in use. The hand-magnifier, B, is the simplest of all simple microscopes: it consists merely of one lens, in a tortoise-shell frame, made to shut up between two other plates of the same material, like a knife-blade in its handle. Sometimes three lenses are thus arranged, and by using one or more of tliem at a 4 MICROSCOPE TEACHINGS. time, the magnifying power is varied. Of this form was the “magnifying-glass” already alluded to, which the writer found very useful before possessing Eoss’s Microscope. The Coddington lens will be seen represented at woodcut No. 3, among the collector’s apparatus, its glass shutting up into a neat little cylindrical fi'ame, with a short handle to which a chain or string can be attached. This instrument, and a good little hand-magnifier, like that shewn at No. 1, B, will be found useful ap- pendages to the watch-chain — always at hand to examine objects out of doors. The Coddington lens has by far the higher power of the two, but from its requiring to be held very close to objects it cannot always be used to advantage. The magnifying-glass becomes a microscope when its lens (or combination of lenses) is fixed to a stand of any kind; and in its complete form it should have a little plate of metal, c, No. 1, called the stage, on which the objects are placed; a mirror, , you see it closing like a fan. Fig. c, shews the two bends which it then takes; and at c?, how tidily it is packed ready to lay along the insect’s back! But let us pause before we hurry it thus out of sight, and turn again to its pictured representation, fig. 2, as shewn through a small magnifying glass. The Aving should be held somewhat obliquely to the light, and tlien the lovely colours, green, blue, red, and golden gleam with a soft radiance. Do you ask the reason why we examine this wing simply with a magnifying glass, instead of with the large microscope? It is because, taking the entire wing, it is rather too large an object to be shewn at once. The lowest poAver of my microscope is twenty diameters, and this object, you see, measures three eighths of an inch in Avidth, so that if magnified to tAventy times that diameter it Avould be sheAvn a length of seven inches and a half, and, turn it as you might, could not be fitted into a page of this book. And here, per- haps, the question may arise, “Is fig. 2 only four times larger than fig. 1, a?” The answer is, it LINEAR AND SUPERFICIAL MEASURE. 39 is four times its diameter^ and this is the measure employed in works on the microscope, and called the “linear measure.” It signifies that the object, when stated to be, as in the present instance, “mag- nified four diameters,” appears four times the height and four times the breadth that the unassisted eye observes it. The representation of the wing at fig. 2, takes up sixteen times the space occupied by fig. 1, a; and that statement of the amount to which it is magnified, is called the “superficial measure,” or measure of the surface, and can always be calculated by squaring the linear measure. Thus the wing represented at fig. 4, being magnified five diameters, is magnified twenty-five times by super- ficial measure, and the object represented at fig. 6, and described as being magnified 420 diameters, occupies a hundred and seventy-six thousand four hundred times more space than that of the minute structure itself. But the “linear measure” is in every way the best and most convenient method of stating the magnifying power employed. The observer, after examining such an object as this earwig’s wing with a magnifying-glass, ivill do well to submit it next to the lowest power of the compound microscope, when probably some minute details may appear demanding still further raagni- 40 MICROSCOPE TEACHINGS. fying. A power of a hundred diameters in a good microscope is one which exhibits a great deal. The little folded wing, fig. 1, d, is nicely shewn with it; its nineteen folds may be seen squarely and neatly laid over each other; you reckon them as a shopman does the yards of silk in a folded piece. Then, see the wing itself with this power, you find it covered with very minute round marks, and fringed round with fine hairs. Beetles do not fold up their wings into so small a compass as those of the earwig, and accordingly No. 5. — Folded Wing of Whirligig Beetle, magnified 15 diameters. the strong ribs or nervures are ditferently arranged. No. 5 represents the folded-up wing of the whirligig beetle, (Gyrinus natator,) a little water-insect, re- markable for its habit of whirling round on the WING OF WHIRLIGIG BEETLE. 41 surface of ponds and brooks.* This wing, when expanded, appears as in fig. 4, Plate I. With this low magnifying power we can detect on its surface some pattern or graining of wmnderful delicacy and minuteness. To examine this, ive apply one of the high powers of the microscope, attending however to the rule, to use the lorcest with which we can clearly see ivhat we require. How exquisite, how delicately finished is the appearance of this little wing. An artist’s eye looks with pleasure on the bold curves and rich brown colour of the large nervures, and the beautiful regularity of the smaller markings. These prove to consist of tens of thou- sands of delicate hairs, while the wing is edged with somewhat longer ones. I have drawn a very small portion of the wing magnified 420 diameters. Were I to represent the entire wing on this scale, I must make it more than ten feet long ; yet it is ornamented with the same beautiful regularity over the whole surface. Will you look, reader, at the real size of the wing, and judge what must be the minuteness of its delicate adornment? In the wasp’s wings, represented at fig. 8, we have to admire their evident adaptation to the insect’s mode of life, as well as their beauty. They * A figure of this beetle will be found in chapter YII, 42 MICROSCOPE TEACHINGS. are not so carefully stowed away as those of the earwig or beetle, as it wants to fly so much more frequently. Yet wasps often go into the ground — and bees (whose wings much resemble those of wasps) creep into very small flowers — therefore a pair of large broad wings would be in their way. The contrivance they are supplied with is very curious. They have four wings, two on each side, and the upper wings fold once, lengthwise (fig. 7) when the insect walks, but when it prepares to fly it straightens this wing by the act of raising it, and the same action hooks the lower wing to it firmly, giving it all the force of a single broad wing. Fig. 8 represents the two wings thus joined, and slightly magnified. To show the minute hooks which are on the top edge of the lower wing (fig. 9, A,) I must take my specimen in which the wings are prepared separated from each other, and will magnify them 60 diameters. The part of the wing on ivhich the hooks are placed is very small, not more than one twentieth of an inch in length. They clasp firmly over a projecting ledge on the upper wing (fig. 9, B.) This is best understood by observing a preparation, (as in fig. 8,) where the wings are mounted ready clasped, and examining them on both sides. Wings, etc., of Insects. Plate 0. 1. Small Dragon-fly. 2. Part of small Dragon-fly’s wing, magnified 7 diameters. 3. Wing of another species of Dragon-fly. 4. Part of wing, magnified 7 diameters. 5. Minute Beetle, common in Spring. 6. Beetle, magnified 30 diameters. 7. Hairs of Beetle, magnified 420 diameters. 8. Wing-case of Beetle, magnified 50 diameters 9. Teeth at the base of wing-case, magnified 900 diameters. WINGS OF DRAGON-FLIES. 43 The dragon-fly’s wings, which never require to be folded up or reduced in size, are formed for strength and lightness, and evidently for beauty too. Plate 11, fig. 1, represents one of the small dragon-flies, so common through the greater part of summer, with bright blue, or oftener red, bodies. Their wings are beautifully transparent, consisting of a delicate membrane, stretched, as it were, to a sort of ornamental network. A small portion of one wing, magnified 7 diameters, is shown in fig. 2. The shaded compartment represents the single dark spot so prettily placed near the tip of each Aving. Another dragon-fly, rather larger, and with a me- tallic-looking bluish green body, has more minute divisions in its Avings, and in each wing a brownish patch of shading, producing a very soft appearance. It has not the little black spot in each Aving; it seems as if that ornament would not be in keeping with its softer shades, (figs. 3, 4.) But the wing Avhich I have always thought the most curious in my collection is that of a little beetle, so small as to possess (so far as I know) no popular name, but Avhich in learned language, boasts an appellation of no less than nine syllables, — “Trichopteryx atomaria.” It is a very lively, active little creature, common under moss in spring; 44 MICROSCOPE TEACHINGS. and is to be observed like the larger insects coming forth in the summer sunshine, and taking short but energetic flights. It is represented of the natural size, and in the act of flying, at fig. 5 ; while at fig. 6 you may see it when magnified 30 diameters. Its wings are unusually narrow, and each fringed Avith hairs half the length of the wing itself. This long fringe surrounds it except in two places at the centre, Avhere the wing doubles up so as to allow it to fold easily; here it is replaced by short hairs. I have a slide, showing the folded wing and its case prepared side by side, and I can see that there is a sharply-creased “plait” or “tuck” in this central part, which shortens the narrow shaft of the Aving; then the point of this shaft is doubled up, then another fold stoAvs all aAvay neatly, and all the longer hairs point nicely doAvnward; while the little wing occupies less space than the wing-case which is to cover it. The hairs on this wing require minute examina- tion. With even so high a poAver as 100 diameters, Ave fail to make them out; but a poAver of 200 shcAvs them to be each fringed again like a feather, (fig. 7,) and the same poAver shews that at the base of each of the little Aving-cases, which measure at their broadest part only one sixty-second of an NATURE S WATCHES. 45 inch, there is a delicate little comb formed with beautiful regularity, and having (as I ascertained with the highest power of my microscope*) one hundred and twenty teeth ! I have made a separate drawing of the wing-case to shew the position of this comb, which extends from A to B, (fig. 8,) a space scarcely more than the hundredth part of inch. I imagine its use may be to remove all particles of dust from the long feathery wings before the wing-cases close over them. Fig. 9 represents a few of these teeth as seen with a power of 900 diametei‘s. The thinly-scattered strong bristles on the wing-case contrast with the regular appearance of the tiny comb. It must have been at the sight of some object such as this that Boyle, the eminent philosopher, remarked that “his wonder was greater at Nature’s watches than at its clocks.” Look again, readei', at fig. 5, and think of the variety of detail to be observed in the organization of that tiny creature, even where attention is drawn to the exterior only, ^ 900 diameters. It may interest the reader to hear that Mr. Spence, the late celebrated entomologist, in acknowledging an account which I sent to him of some of the above objects, wrote, “I was especially pleased with the figure and description of the comb-like appendage to the elytra [wing-cases] of the minute beetle, so admirably figured, of the existence of which appendage I was not at all aware, never having examined this species with a powerful lens.” 46 MICROSCOPE TEACHINGS. and to the wings and wing-cases alone ! Is it not truly said that a close scrutiny of God’s works conveys with it an awful, overpowering sense of a presence and a power more than human? and evinced no less in the smallest than in the greatest of His works. For they are alike created by One who judges not as we do of great and small; who “taketh up the isles as a very little thing,” and counts the nations as “the small dust of the balance;” and yet promises to each individual of those na- tions — to any man who loves Him, and therefore keeps His words — that He will “come to him, and make His abode with him !” While we are enabled, with the microscope, — “To trace in Nature’s most minute design The signature and stamp of power divine, — we may profitably follow up the thought our Lord Himself suggested. He will much more clothe us than the grass and the lilies of the field, beautiful though they be; and we are in His sight of more value than many sparrows, though not even a sparrow falls to the ground without His knowledge. And He will not fail to order the events of our lives in the very best way, when His skill is so unerring and His providence so kind in the for- mation of the smallest insect. WINGS OF MOTHS AND BUTTERFLIES. 47 CHAPTER V. SCALES OF INSECTS AND FISH. The wings of moths and butterflies are actually very like those of flies and wasps, etc. They are thin and transparent in themselves, but covered on both sides with beautiful scales, laid in rows like the feathers on a bird, each row, in the generality of specimens, overlapping a portion of the next, so as to give to their surface, when sufficiently mag- nified, very much the appearance of being tiled like the roof of a house. Each scale has a small foot- stalk, (Plate III, fig. 8, and Plate IV, fig. 10,) which fits into a minute socket on the transparent membrane of the wing. The arrangement of the minute sockets is well shewn by making a prepa- ration of a butterfly’s wing nearly divested of its scales. A good deal of washing and rubbing Avill be found necessary to remove them, and then the object is one from which, when dry, mounted on 48 MICROSCOPE TEACHINGS. a slide, and viewed by transmitted light, a good deal may be learned. But the wings in their natural condition, viewed as opaque objects, are among the most lovely spectacles presented to us by the microscope. Their appearance strikes us with new wonder, as we observe the beautiful harmony of their hues, and the elegance of their adornment. The wings are the only part generally mounted for the microscope ; but if a whole butterfly is examined, which may be safely and easily done by removing one from an entomologist’s collection and sticking its pin into a morsel of cork, which is generally to be found in the handle of the stage forceps, it will be seen that the whole bodies of these insects also are clothed with scales. In exhibiting the wings of moths and butterflies the effect is much heightened by a proper ar- rangement of the light, which should be placed so as to throw an artistic shadow from every scale. This suggestion may seem a trifle, but the trite maxim concerning trifles tending to produce per- fection will excuse its being made. Fig. 2 shews the scales of a moth very common on fine evenings in June, called the “ghost moth;” they are very like bay leaves in shape. The scales The Microscope, and Wings of Moths. Plate 3, 1. The Microscope. 2. Scales of Ghost Moth, magnified 80 diameters. 3. Scales on the under side of Ghost Moth’s wing, magnified 100 diams. 4. Green Forester Moth. 5. Scales of Green Forester Moth, magd. 100 diams. 6. Scale, magd. 300 diams. 7. Six-spotted Burnet Moth. 8. Scale of Burnet Moth, magnified 420 diameters. w m X GREEN FORESTER MOTH. 49 on the inside of the wing are different, and thinly scattered, (fig. 3.) The wings of this moth are yelloAvish, having (on the upper sides) what look like delicately-painted streaks of pink; these are red scales. Some of the scales of moths and butterflies will be admired for their delicate hues; others shine with a brilliant metallic lustre, to which the best painted representation could scarcely do justice. The “little green forester moth” (fig. 4) is one of these; it has scales of two different shapes on its wings (fig. 5,) the longer being brilliant yellowish green, and the shorter bluish green. When highly magnified, the scales of this moth are seen to be covered with a sort of ornamental carving; each of the larger scales has six or seven ridges on it, and rows of hollows between (fig. 6.) The smaller scales are very similarly ornamented, with a pattern not quite so much raised. This little moth is common in the beginning of June. There is another, somewhat like it in shape, and still commoner at the same time of year; it is called the Burnet-moth, (fig. 7.) Its upper wings are of a beautiful, very dark green, with round red spots; its lower wings red, edged 50 MICROSCOPE TEACHINGS. with bluish black. The dark green scales are glossy like satin, and the red very bright in colour, but dull like cloth or flock paper. This variety of surface forms a very striking contrast. The dark scales of the Burnet-moth are sculptured in a way similar to those of the green forester. When these scales are viewed as transparent objects, they no longer appear green, but the pattern on them, when viewed with a high magnifying power, assumes a strange and almost startling appearance. It must be remembered how small these scales are. They are only like the finest dust or powder, and a single one could scarcely be seen with the naked eye. Yet every scale may be seen (with a magnifying power of 150) to be marked with some dozen lines, clear and sharp as staves of music, and between them are rows of characters wonderfully resembling some old Babylonish inscrip- tion, (fig. 8.)* The scales of the green forester moth are somewhat similarly inscribed, but not with equal distinctness. Let us again adjust the microscope to view * The figure represents this object magnified 420 diameters, not 150. It could, however, be sufiiciently well seen with the latter power, although the additional size gained by further magnifying makes it easier to engrave. The same remark applies to many other objects represented in this work. ARRANGEMENT OF SCALES. 51 “opaque objects,” and feast our eyes on a few more specimens of Nature’s mosaic work. The wings of butterflies and moths have been compared to patterns in mosaic; though of course there is this great difference, that the pieces of mosaic are inlaid; whereas the scales of these insects, as I have already said, lie over each other like feathers, fishes’ scales, or tiles on a roof. Still their general flatness, and the fact of their delicate shades being usually caused by hundreds of minute scales— the dark or light ones in greater or less number according to the hue required — originated the comparison. I have examined some, however, in which the effect of the shading is heightened in a way in- admissible in mosaic work, but sometimes employed by painters. It sometimes happens, that when an artist is painting, — for instance, a landscape, — and wishes to bring out a rock or tree very vividly, he finds it necessary to make a roughness on that part of his canvas. A painter, whose works are familiar to many, on one occasion actually made the surface of his picture rough by causing a small quantity of sand to adhere to the canvas, and it had the desired effect of giving brightness to what was then painted over it. y, OF ILL UB. 52 MICROSCOPE TEACHINGS. Now there is a yelloAvish-brown insect called the Herald-moth, with one conspicuous white spot on each of its upper wings, shining like a star, or with the peculiar brightness that this representation of it (Plate IV., fig. .1) would exhibit if we were to priclc it with a pin and hold it up to the light. On examining it with the microscope, I found that this spot consisted of a thick tuft of white scales, almost like a little brush, and standing up much higher than the surrounding parts of the wing, (fig. 2.) In like manner the scales of the Emperor-moth, a large insect with an eye-like spot in each wing, are rendered much more ornamental by being set sloping upwards instead of nearly level. There is a beautiful semi-transparency in the wings of this moth, owing to the thinness with which its scales are scattered; but their sloping arrangement gives brilliancy at the same time. It is, of course, difficult to represent it on a flat piece of paper. , The eye-like spots are each about the size of fig. 3, and fig. 4 is intended for a small part of one of them, magnified 60 diameters. The colours are white, morone crimson, a sort of straw-colour, and black, a beautiful and harmonious mixture. I have noticed another deviation from the plan of mo.saic work iti the win