Every Boy's Book: A Complete Encyclopædia of Sports and Amusements

by Unknown

THE MICROSCOPE.

At any time of the year or hour of the day there are few pursuits more interesting, and at the same time instructive, than the study of Nature by means of the microscope.

This instrument has revolutionized science, solved many problems that had wearied the souls of older naturalists, and even in its simplest form is beyond all value to those who love Nature and the objects which they see around them. The microscope opens a new world to us. When the first telescope was directed to the heavens, and unlocked the mysteries of the skies, when it crumbled into dust all the theories of the past centuries, and told mankind that the planets were not merely instruments of fortune-telling, whose voices were intelligible to a chosen few, but orbs far vaster than our own; even then the new world of thought into which man entered was no wider than that which is displayed by the poorest lens that possesses the power of magnifying.

All of us must admire the more than awful grandeur of that universe whereof we form so infinitesimal a part, wherein the stars are scattered as the sand on the sea-shore, and every star a sun, the centre of a system of orbs too distant for the eye of man to perceive. Looking at our nearest planet, and observing on her face vast mountain-chains, ravines into which the light of the sun can never penetrate, and volcanoes whose craters are so wide that they would take in the whole of London, the whole of Birmingham, and all the country between them, we can judge by analogy of the unseen wonders which must exist in the world beyond our ken.

But to him who can read Nature rightly, the microscope is a teacher as grand as its sister instrument, and the awful magnificence of Nature is as evident in a midge’s wing as in the more patent glories of the sun, moon, and stars. In the following pages we hope to put the readers of this book in the way to read their microscope rightly—possibly to make it—and to show that much can be done with small means when “there’s a will,” and to indicate to them that objects of no small interest can be found without stirring from the room in which we sit, or even from the table on which our microscope is placed.

Some of our readers may say, when they read the heading of this paper, that they should like a microscope very much, but that they have no money to buy it, and that their parents cannot afford one.

This is just the feeling which we used to have when a boy, for in those days microscopes were microscopes indeed, and you had your choice between a little instrument, with a series of brass cups, having glasses in them, which magnified slightly but defined clearly, or a great composition of brass and iron, looking like a rocket-tube, with an eye-piece at one end and a glass shot at the other. In was very costly, very imposing, and magnified very highly; but it strained the eyes painfully, had no defining capacities, and made all the objects look as if they were seen through a thick fog. Practically, therefore, the former was the only instrument that was available.

A still more useful instrument, however, was that which can always be obtained for a few shillings, and which is now made wonderfully cheap and wonderfully good; we mean the double or treble pocket-lens. So we say, if you cannot afford a really good microscope, do not waste your money upon inferior and pretentious instruments, but get a sound pocket-lens.

It has a thousand advantages. It is portable, and is even more useful in the fields than in the house. It defines very clearly, and needs little trouble in manipulation. We need not say how difficult is the task of getting a complicated instrument to define properly, how impossible with a bad one. The object and the glass can be held in any light,—a matter of no small consideration when examining anything new, and trying to make out its structure. It is not easily put out of order, and if treated with the most ordinary care, will last for a lifetime.

You can push it under water, and it will magnify as well as in the air; and if you are wandering on the river-side, you can lie down on the bank, dip the upper part of your head into the water, together with the glass, and watch carefully the subaquatic objects without removing them. The water will not hurt the eye in the least, though a non-swimmer may perhaps find a little difficulty in his first attempt. It makes a good burning-glass, should fire be needed, and no other means of procuring a spark be at hand. It can be used so as to show the principle of a camera obscura, and to illustrate the manner in which photographic portraits are taken. It can be made into an admirable dissecting microscope, and needs scarcely any practice in the manipulation. These are some of its advantages, and there are many others which need not be mentioned.

Even if you should be able to procure a good microscope, get a pocket-lens as well, for you will want them both, and we may say that the most practised microscopists, and those who are possessors of the most elaborate instruments, are the very men who are most certain to have a pocket-lens about them, and to use it most frequently. Practise well with the pocket-lens before you meddle with the compound microscope. You will waste no time, but will rather gain by it; for you will be learning the rudiments of a new science, and laying a solid foundation on which to build. Whenever we see a lad take out his pocket-lens in a business-like way, use it skilfully, and put it back with a mechanical facility that tells of constant practice, we know that there is a lad who has learned the chief lesson of a naturalist,—namely, the art of observing. We speak highly of the pocket-lens, because we think highly of it and owe much to it.

One or two practical remarks on the proper handling of the pocket-lens may be of use. Do not always employ the same eye in looking through the lens, but use the eyes alternately. There is always a temptation to employ the same eye, which thus receives a kind of training in vision; but it is a temptation always to be resisted. With some persons the right eye is most in favour, and with others the left; and when the favourite eye gets all the work, it too frequently suffers. Whether you look with the right or the left eye, keep both eyes open.

It is a pitiful sight to see a human face all screwed up into a corner, the lids of the unused eye convulsively squeezed together, and the mouth slanting upwards, as if in sympathy with the eye. Not only does the human face become repulsively mean and portentously ugly by such action, but the sight of the eye is seriously strained, and sometimes impaired for life. At first the beginner will find a little difficulty in restricting his vision to one eye while the other remains open, just as a beginner on the pianoforte feels himself puzzled when he tries to make his right hand go one way and his left hand another; but in either case a little practice and plenty of perseverance are sure to overcome all obstacles, and in a wonderfully short time the difficulty will not only be overcome, but forgotten.

We speak here with some feeling, because, while engaged on a work on the microscope, we were necessarily obliged to work much at night, and inadvertently employed the left eye more than the right; the consequence of which imprudence was that we have been obliged ever since that time to give the left eye perfect rest, as far as artificial vision goes, and, except when looking through a binocular instrument, we have not ventured to use it either to a microscope or telescope. The vision accommodates itself to circumstances with wonderful ease, and the observer learns the curious art of cutting off all communication between the unused eye and the brain; so that, although the objects around may imprint themselves upon the retina, the mind is as totally unconscious of them as if they had no existence.

If possible, always examine an object without removing it, as thereby you see it as it is, without altering any of the conditions with which it is surrounded. Should this not be practicable, take the object to be viewed in the left hand and the lens in the right. Place the wrists of the two hands together, and then you will find that one supports the other, and that the lens can be held in the proper focus without the least difficulty. After you have used the lens for some little time, you will learn to hit upon the right focus almost to a hair’s breadth,—so as to lose no time, a matter of some importance when a living creature is to be examined, especially if it be in motion.

As to the selection of objects, none is necessary. Look at everything; and the uglier and more unpromising it is, let it be the closer examined. We do not merely use our aids to vision for the sake of seeing beautiful things, though the microscopist sees more beauty in a day than others will see in a year. We want to see how the world and its constituent parts are made; and though admiration will not be wanting, yet it does not, or ought not, to hold the first place. Always have a motive for looking at every object, and if you have none, try to make one. One of our friends, known by name at least to most of my readers, struck out, some years ago, a most curious train of thought while looking at an object which is seen daily by thousands of human beings, and will probably soon give the public the benefit of it. We have seen the object hundreds of times, but the ideas which it suggested did not happen to occur to us.

We are now about to suggest a very simple piece of mechanism, by which the pocket-lens can be converted into a microscope that will serve for dissection and many other purposes. The accompanying [sketch] is taken from an instrument of our own manufacture. It is of very rough make, and by an old Indian officer would be contemptuously termed “cutcha.” Measured, however, by its performance, it is quite as satisfactory as those instruments which are made by professed opticians, and which the same old Indian would class under the honoured title of “pucka.”

Melt three or four pounds of lead in an iron ladle, and make a mould, consisting of a hollow hemisphere of paper or cardboard, through the centre of which an iron rod has been passed. The hollow of the paper should resemble an ordinary saucer. Pour the lead into the saucer, and let it cool. The paper mould will be scorched by the heat and rendered useless, but an outer coating of lead will be cool and hard before the paper is quite destroyed. The rod and leaden stand will now appear as in the [illustration]. Next take a piece of stout brass wire and a wine-cork; twist the wire round the cork several times; cut off one end close to the cork; sharpen the other, and turn it up as seen in the [engraving].

Bore a hole through the cork, just large enough to allow the upright rod to slip through it, and there is the “stand” of your microscope. Now take your pocket-lens, and get an optician to bore a hole through one end of it, just large enough to receive the upturned end of the wire; slip the lens on the wire, and the microscope is complete.

The cork, though grasping the upright stem with tolerable firmness, can be slid up and down so as to insure the correct focus, and can be pushed aside whenever the object has to be viewed with the naked eye and must not be removed from its place. This instrument is a capital one for dissecting purposes, and will answer quite as well as those expensive affairs that are to be purchased in the shops. If, however, our readers would like to possess a real and well-made instrument, he cannot do better than get one of Ross’s Dissecting Microscopes, which are very steady, and, [as may be seen], can be adjusted to almost any position. A rack-and-pinion movement for elevating or lowering the sliding pillar would be useful.

ROSS’S DISSECTING MICROSCOPE.

If the object be transparent, and requires to be seen by transmitted light, the following plan will answer:—Take a thin piece of wood, cut or punch a round hole out of the middle, and support it on four legs. Wires or wooden pegs fixed in corks will answer the purpose well, and if the corks be glued to the corners of the board, the legs can be inserted or removed at pleasure. The wood of which cigar-boxes are made will answer the purpose very well. Its dimensions should be about three inches in length by two in width. Now buy one of the doll’s looking-glasses that are sold for a penny, and put it under the stand. Lay a flat piece of glass over the hole, place the object upon it, and direct the light through it by means of the mirror below. If such a mirror cannot be obtained, it is easy enough to make one, by mounting a piece of looking-glass in a cork frame, and making it swing on pivots, like the glasses of our dressing-rooms.

The young microscopist must remember that when he is examining any object by transmitted light, he must arrange it as flatly as possible on the glass. In many cases, a still neater manipulation is required,—as, for example, when the petals of flowers are under examination. Thin glass is to be purchased at any optician’s, and if cut in squares, instead of circles, is very much cheaper, and quite as useful for all practical purposes. Lay the petal on the glass plate, place a piece of the thin glass upon it, and press it gently while examining it. If it still remains thick and dull, put a drop of pure water on the petal, and replace the thin glass, when the structure will almost invariably be detected.

Everything depends on the proper management of the object and the arrangement of the light. Some opaque objects can be seen best by direct light, and others by transmitted light. If a leaf be examined, particularly if it be a thick and heavy one, like that of the ivy, the upper and lower membranes must be stripped apart,—a task which is easily performed by tearing a small slit, and then ripping it smartly across. A pair of forceps will be required for this and other delicate work, and may be obtained at a cheap rate. Care must be taken to keep the points exactly even, and if at any time one of them appears to be shorter than the other, they should be rubbed on a hone until they are brought perfectly level.

These should be made of steel; but the young microscopist will find that a second pair made of brass, and much rougher in finish, are invaluable aids as he takes his walks into the country. By their aid he can pick up minute objects, draw insects out of crevices without damaging them, and pluck the tiniest flowers without harming their petals. They can be carried in the waistcoat pocket, and the cost is sixpence. Any lad who knows how to handle solder can make a pair for himself in a few minutes.

A penknife with one blade kept scrupulously sharp is essential, and we have found an old lancet of the greatest service. Lancets have gone so much out of fashion, that the second-hand instrument shops abound with them. We did not allow our own lancet to be shut up, but removed the blade from the tortoise-shell handle, and fixed it upon a wooden handle, about four inches in length, so that it looked very clumsy, but was extremely useful.

Two pairs of scissors are needful,—one very fine, and the other moderately strong. Both pairs, however, must have very short blades and very long handles, and the scissors such as ladies use are of very little use, the short handles causing the fingers of the right hand to shade the object. As to the fine pair, it is hardly possible to have the handles too long or the blades too short; for if the points can be separated a quarter of an inch, nothing more is needed. If a pair of bent scissors can also be obtained, they are extremely pleasant to work with, and save much trouble.

For arranging the objects under the microscope, there are no instruments equal to those which are [here engraved]. They are nothing more than ordinary needles stuck into the handles of camel’s-hair brushes. The uppermost is made of the largest-sized darning-needle, and is useful for making little holes, and similar purposes. The two next instruments are the most generally useful, and several of each should be always at hand. Nos. 4 and 5 are for special purposes; the former for holding tissues aside, and the latter for lifting them up. The needles must not be longer than those in the illustration, as they would otherwise be too springy, and apt to tear the object instead of pulling or pushing it.

The bending is readily done in the flame of a spirit-lamp, or even of a common candle; but in the latter case the needle is always covered with soot, which must be wiped off before its shape can be seen. The elasticity of the needles is lost by the operation, but is easily restored by heating them red-hot, and plunging them immediately into cold water. The end of the handle should be wrapped with thread, in order to prevent it from splitting.

Pill-boxes of various sizes are of very great service to the microscopist. We always have them arranged in “nests,” i. e. six or seven inside each other, so that space is greatly economized, as long as they are not in absolute use. All delicate objects should be placed in separate boxes, and the predaceous insects must be treated in the same manner, or they will certainly destroy one another, or, at all events, inflict such injuries as will make them useless for microscopic purposes.

When the insects are to be killed on the spot, we employ another and a very simple plan.

We take one of the old-fashioned wooden lucifer-match boxes, bore a hole in the lid, and push through the hole a swan-quill or the barrel of one of the swan-quill steel pens. A glass tube is still better, but is too fragile. Beeswax is tightly worked into the junction of the tube with the wood, so as to make it as nearly air-tight as possible. A cork stopper is then cut to fit the tube. The accompanying [illustration] will show the box completed. When this is finished, we take the smallest-sized pill-box, bore a number of holes in it with a red-hot needle, place a little piece of solid ammonia within it, and inclose it in the lucifer-box. Its effects are almost instantaneous; for scarcely has the insect touched the bottom of the box before it is helpless, and in a very few moments it is quite dead, so powerful is ammonia towards insects. The reader will of course understand that the pill-boxes must never have been used for pills, and that the match-box must be carefully cleaned before employing it in the microscopic service. Moreover, any boxes that have been used for lepidopterous insects become useless, inasmuch as the scales always fall from the wings, and cling to the sides of the box, so as to mix with succeeding objects, and very much puzzle the observer.

Aquatic and marine objects require bottles, and, as a general rule, these bottles ought always to have wide mouths. Indeed, if there be no shoulder at all, their purpose will be better served, as a small object is very apt to be caught under the shoulder, and to give much trouble before it can be removed without injury. Wide and short test-tubes answer admirably for collecting; and it will always be advisable to have a few small test-tubes ready fitted with corks, for the purpose of isolating those specimens which might receive or cause injury by being mixed with others.

To remove minute objects from one vessel into another is a very easy process. Take a glass tube, mark off a portion about eight inches in length, cut a little notch with a file, and bend it smartly, when it will break neatly across, without leaving points or having the regularity of its ends injured by gaps. Turn each end round and round in the flame of the spirit-lamp, and you have an ordinary “pipette.” The object of placing the ends of the tube in the flame is to render the edges quite smooth and rounded.

Now mark off the same length of tube, and place the marked portion in the flame, taking care to warm it well first, lest the sudden heat should crack the glass. Keep it continually turning between the fingers, and when it is quite soft, and of a fine red heat, draw the hands smartly apart, and you will produce a couple of tubes tapering to very fine points. Break off the tapering portions at any convenient point, round the edges as before, and you will then have pipettes suitable for small objects. As there are many specimens, especially the smaller animalculæ, which have a habit of retiring into the remotest corner, it is necessary to bend another pipette, so as to follow them. For our own part, we prefer the pipette to be bent nearly to a right angle.

The mode of using these simple instruments is as follows:—Place the forefinger or thumb firmly on the large end, and push the point under water. When the opening is close to the sought-for object, lift the finger suddenly, and admit the air into the tube. The water will immediately rush in at the lower end, and if the orifice has been properly directed, will carry the object into the tube. The finger is again applied to the mouth of the tube, and the object can be then carried off.

As with the pocket-lens almost every object is to be viewed by means of direct light, the young observer will find himself much aided by a suitable background. Any small object, such as a minute insect, a seed, or a hair, becomes very indistinct if held up against the light, or even when viewed against a broken background of trees, houses, or herbage. The simplest plan of securing a proper background is to take a disc of ivory, bone, or even of white cardboard, and to blacken one side of it. The black paint which is used for this purpose must be without gloss, and have what is called a “dead” surface. Ink answers very well for the purpose, and so does ivory-black; but Indian ink is too glossy to be serviceable.

To procure specimens from the water is a matter of some difficulty if managed badly, but easy enough when the collector knows his business. It is of course needful to attach the collecting vessel to the end of a rod, and to plunge it into the spots which look most favourable. Now even so simple a matter as this requires some little care, if the young microscopist really wishes to obtain the best specimens. A common walking-stick will answer most purposes; but the most efficient rod for the purpose is one of the common walking-stick fishing-rods without the top joint, as it can be carried without attracting attention, and can be lengthened at will by adding the different joints.

Many methods have been proposed by which the vessel is to be attached to the rod; but that which I am about to describe is certainly the simplest and most effective that I have tried. Get a piece of gutta-percha tubing, just large enough to be slipped on the end of the rod or stick; mark off an inch or so, and cut the tube nearly through, as at a in [Fig. 1]. Now cut it away longitudinally, so that a long tongue of gutta-percha is left, as at b, and the instrument is completed.

Its application is as simple as its structure. Bend the tongue over, so as to form a loop, and push the end through the short tube. Slip the neck of the bottle into the loop, and draw the tongue until it is tolerably tight. Push the end of the stick into the tube, taking care to hold the tongue firmly in its place, and the vessel will then be fastened at right angles to the stick.

The whole arrangement can be seen in [Fig. 2], where a represents the gutta-percha tube, b the tongue, c the stick, and d the vessel.

The method of collecting by means of this instrument is as follows:—Immerse the vessel in the water, with the mouth downwards, so that no water may enter. Push it gently towards the spot which is to be investigated, move it about a little, so as to cause a disturbance, and then turn the vessel with its mouth upwards. Water will instantly rush in, carrying with it the objects which are to be examined. The contents of the vessel may then be transferred to the large bottle, and another dip made. Confervoid growths, especially those which accumulate in a kind of scum on the surface, should be obtained very quietly, without previous disturbance of the water.

After the pond or stream or ditch has been well searched, the bottle should be roughly examined, by means of a pocket-lens, and the contents sorted into the smaller tubes, as has already been mentioned. This precaution is especially needful when any of the minute crustacea called Entomostraca are captured, as they are most voracious beings, and will make sad havoc among other specimens, unless they are placed in separate bottles. They are mostly large enough to be detected with the naked eye, and look something like little fleas, as they move along.

As the Entomostraca cast their shells repeatedly during their lives, some species performing this operation every two days, a beautiful series of objects can be obtained by gathering the cast shells, and preparing them for the microscope, according to the directions that will be found in the following pages. These shells are peculiarly valuable, as they retain the chief external characteristics of the creature to which they belonged, the limbs, plumes, and even the delicate bristles being preserved entire. It is in the power of the microscopist to retard or hasten the change of shell, heat and light aiding development, and cold and darkness retarding it. The remarkable “ephippium,” or saddle, which is found on the backs of the Daphnia, the Moina, and other Entomostraca, and which is used as a receptacle for eggs, should be searched for and preserved.

A very thin and very flat bottle is a most useful assistance in detecting the character of any unknown object, especially if it be living. Such a bottle may easily be made by heating one of the small test-tubes in the spirit-lamp until it is of a glowing red heat, and then pressing the sides together. Some little neatness is required in this process, as an unskilful operator is apt to press the sides unequally, and to leave a bulging projection at the end.

Should a higher power be required than is furnished by the pocket-lens, a “Coddington” lens is the very best that can be obtained. In general shape it resembles the well-known “Stanhope” lens; but the latter is so very inferior an article, that it ought never to be purchased. The two glasses can easily be distinguished by the shape of the ends; those of the Coddington being alike, while in the Stanhope one is much more convex than the other.

At first the young observer generally finds some difficulty in arranging this lens, so as to hit off the focus exactly; but if he adopts the following plan, he will soon handle a Coddington as easily as an ordinary pocket-lens. The object should be held in the left hand and the glass in the right. Let the wrists be placed firmly against each other, and the lens brought as close as possible to the object, without quite touching it. Now bring the eye to the lens, taking care not to disturb the arrangement, and then gradually draw the object away from the lens. The moment that the proper focus is obtained the object will be seen with beautiful clearness, and by drawing the object from the lens, instead of approaching the lens to the object, there is no danger of injuring the one or the other by contact.

The great advantages of the Coddington are the exceeding clearness with which it shows the object, the perfect definition of every line, its achromatic character, and its freedom from colours, and the flatness of the “field;” so that the circumference is defined as perfectly as the centre. It can now be obtained very cheaply at any of our microscopical opticians, and should always be mounted on a tolerably long handle.

THE COMPOUND MICROSCOPE.

We have already described the simpler forms of magnifying instruments, together with the best method of using them. We now purpose to describe the more complicated instrument called the compound microscope, and hints will be given as to the best method of making preparations for it.

The great distinction between the simple and compound microscope is, that whereas the former instrument magnifies the object, the latter magnifies the magnified image of the object. In the least elaborate form of this instrument there are two glasses, one at each end of a tube, the small glass magnifying the object, and being therefore called the “object glass,” while the other, which magnifies the image of the object, is placed next to the eye, and is therefore termed the “eye-glass.” In practice, however, this arrangement is found to be so extremely defective, that the instrument was quite useless, except as an experimental toy; for the two enemies of the optician, chromatic and spherical aberration, prevailed so exceedingly, that every object appeared as if surrounded with prismatic colours, and every line was blurred and indistinct.

In this uncertain state the compound microscope remained for many years, its superb capabilities being scarcely recognised. The chief fault was thought to be in the material of which the object-glass was made, and for a long series of years all experiments were conducted with a view to an improvement in this respect. When, however, the diamond had been employed as an object-glass, and had failed equally with those of less costly material, attention was directed to the right point—namely, the arrangement of the different glasses,—and at length opticians succeeded in obtaining a pitch of excellence which can be almost termed perfection. It would be impossible to describe the method which is employed for this purpose, and it must suffice to say that the principle is that of playing off one defect against another, and so making them mutually correct their errors.

The magnifying powers of the compound microscope can be very great, and it is therefore necessary that extreme care should be taken in its manipulation. It will be possible for a clumsy person to do more damage to a good instrument in three minutes than can be repaired in as many weeks.

Before proceeding to the management of the microscope and the construction of the “slides,” we will briefly describe one or two chief forms of the compound microscope.

The accompanying [illustration] represents the simplest form of the compound microscope as at present made. It consists of a stand and a sliding tube, in which are set the glasses which magnify the object and its image. At the top is the tube, which is capable of being slid up and down in the shoulder of the stand, so as to obtain the proper focus. Above is seen the eye-glass; and the object-glass is shown at the bottom of the tube. Below the object-glass is the “stage” on which the object to be magnified is laid; and lowest of all is a mirror, which serves to reflect the light upwards through the object, and which can be turned by means of the knobs at the sides. The object-glass is composed of two pieces, which can readily be separated. If both are used, sufficient magnifying power is gained to show the scales on a butterfly’s wing and similar minute objects; while, if one is removed, the object is not magnified to so great an extent, but a larger portion can be seen, and the definition is clearer. The cost of this instrument, together with a few accessories, is half-a-guinea.

There is another microscope constructed on the same principle, which is a very superior instrument, though it does not at first sight present any remarkable difference. It possesses, however, four times the magnifying power of that which has just been mentioned. Instead of two magnifiers, there are four, and several subsidiary articles are sent with it,—such as a condenser, a live box, an aquatic box, and half a dozen slides ready prepared. This instrument costs one sovereign.

But if the reader can by any possibility afford it, let us advise him in the strongest terms to devote three guineas to the purpose, and get a really good instrument. For this small sum a microscope may now be obtained which could not have been purchased for twenty times three guineas only a few years ago. One of these beautiful instruments is seen in the accompanying [illustration]; in which may be seen the tube, with its eye-piece and object-glass, and the stand, containing the stage and the mirror. The arrangement, however, is very different; for the focus is not obtained by sliding the tube up and down, but by turning the large milled heads which we see on a level with the stage, and which raise or depress the tube by means of a rack and pinion. As an extremely high power can be used with this instrument, a still finer adjustment is required, so as to obtain a very accurate focus. This is seen on the front of the tube. The reader will notice that the microscope can be inclined backwards, for it is so made that it can be set to any angle which may best suit the observer. The value of this arrangement is very great, as it permits the observer to sit at his ease in a chair, without being forced to crane his neck over the microscope, and look perpendicularly down. Another advantage attending this arrangement is that the secretions which lubricate the eye do not interrupt the vision, as is apt to be the case when looking directly downwards.

The mirror, too, can be turned in any direction, and its distance from the stage lessened or increased by means of a draw-tube. Three different powers are supplied with this microscope, together with a live-box, dissecting and stage forceps, &c.; and the whole is made so as to admit of additional apparatus. The microscope fits into a neat square box, in which is plenty of room for various articles which will presently be described. These three microscopes can be obtained from Messrs. Baker, 244, High Holborn; and we mention them, not because we wish to make any invidious distinctions between the many excellent opticians who now make microscopes, but because we happen to have used Messrs. Baker’s instruments for some years, and can bear practical testimony to their performance.

Another three-guinea microscope ought, however, to be mentioned. It is the Society of Arts microscope, which is made by Messrs. Field, opticians, of Birmingham. In form it closely resembles the instrument which has just been mentioned, but differs in some of the details, as it possesses a “diaphragm-plate” under the stage for regulating the admission of light, and, instead of three object-glasses and one eye-piece, has two object-glasses and two eye-pieces. Dr. Carpenter mentions that, up to 1861, no less than eighteen hundred of these microscopes had been sold. To this instrument the medal of the Society of Arts was awarded.

Either of these microscopes affords all that an ordinary observer is likely to need; and if he adds a few articles of supplementary apparatus, he will find himself possessed of a microscope that will serve all purposes except scientific controversy.

Presuming that the reader has supplied himself with one or other of the compound microscopes, we will proceed to show the method of using them.

The manipulation of a compound microscope is not so easy as it looks. The possessor of a really good instrument may fail hopelessly in his attempts to see a single object. Now, there are three essential points which a microscopist must attend to,—namely, the correct focus, the proper light, and the preparation of the object. Of these the focus is of course the most important, and can be best obtained as follows:—

Lay the object on the stage of the microscope, so as to get its centre exactly under the centre of the object-glass, and illuminate it as you best can. Put on the lowest power, and, without looking through the tube, lower the object-glass until it nearly touches the object. Now look through the tube, and raise the object-glass gradually from the object, until the right focus is obtained. The reason for taking these precautions is, that if you look through the tube and lower it upon the object, you will in all probability push the glass against the object, and damage either the one or the other. When you have thus learned the focus of the lowest power, add another, and repeat the process; and so on until you have made out the focus of each object-glass. If you have more than one eye-piece, try them both with each object-glass.

The proper light is our next point, and upon it rests the chief beauty of the effect. The light which will suit one object will not suit another, and even the same object should be examined under every variety of light. Some objects are best shown when the light is thrown upon them from above, and others when it is thrown through them from below. Again, the direction of the light is of vast importance; for it will easily be seen that an oblique light will exhibit minute projections by throwing a shadow on one side and brilliancy on the other, while a vertical illumination would fail to show them. On the same principle, one object will be shown better with the light in front, and another when it is on one side.

One of the most effective means of attaining this object is by using the “bull’s-eye condenser,” which is sometimes fixed to the stage, but is usually detached, as represented in the [illustration]. As the upright stem is telescopic, the glass can be raised to a considerable height, while the joint and sliding-rod permit the lens to be applied at any angle which promises the most brilliant light.

As for the kind of light that is employed, there is nothing which equals that of a white cloud; but as such clouds are rare, and are at the best extremely transient, and can only be seen by day, various artificial methods of illumination have been invented. Novices generally think that when the sky is bright and blue they will be very successful in their illumination, and feel grievously disappointed at finding that they obtained much more light from the clouds, whose disappearance they had anxiously been watching. Finding that the blue sky gives scarcely any light at all, they rush to the other extreme, turn the mirror towards the sun, and pour such a blaze of light upon the object, that the eye is blinded by the scintillating refulgence, and the object is often injured, because the mirror is capable of reflecting heat as well as light.

In the daytime there is nothing better than the “white-cloud illuminator,” which is made easily enough by means of plaster of Paris. A sheet of thin white paper fastened against a window-pane is also useful; and the simple plan of dabbing the glass with putty will have a beneficial effect in softening the light, when the window has a southern aspect. In default of these conveniences, it will be often sufficient to fix a piece of white letter-paper over the mirror, or even to dull its surface with wax. At all events, he who aspires to be a true microscopist must be ready with expedients, and if he finds himself in a difficulty, he must summarily invent a method of obviating it.

At night a lamp is necessary; candles are useless, because they have two faults—they flicker, and they become lower as they burn. The latter defect can be cured by using a candle-lamp, but no arrangement will cure the flame of flickering; it is peculiarly trying to the eyes, and destructive of accurate definition. An ordinary moderator lamp answers pretty well, and a small one is even better for the microscopist than one of large dimensions. The chief drawback to the moderator lamp is, that the flame cannot be elevated or lowered, so that the only way to procure a light at a higher elevation, is to stand the lamp on a block of wood or a book. Small lamps are, however, made expressly for the microscope, and, if possible, should be procured, and used for no other purpose, and intrusted to no other hands.

If you want a really brilliant, clear, white light, you must trim the lamp yourself. A small piece of pale blue or neutral-tint glass, interposed between the lamp and the microscope, has a wonderful effect in diminishing the yellow hue which belongs more or less to all artificial lights which are produced by the combustion of oil or fat. We have no doubt but that in a few years we shall be rid of the clumsy and dirty machines that we call lamps, and have substituted for them the pure brilliancy of the electric light.

Whatever lamp you use, a shade is absolutely necessary, in order to defend the eyes. Let me here warn my young readers, that they cannot be too careful of their eyes. In the exuberance of youthful strength and health we are too apt to treat our eyes as unceremoniously as our digestion, and in later years we awake to unavailing repentance.

Many shades can be purchased; but it is far better to make your own after the shape [here] exhibited. They are not pretty to look at, but they save the eyes better than any other form, and whether for reading, writing, or microscopic work, you should use no other. The peculiar merit of them consists in the fact that the light is thrown on the spot where it is wanted, and is cut off from everything except that spot.

Another point which calls for extreme attention is the perfect cleanliness of the glasses. It is astonishing how a tiny dust-mote, or the least condensation of damp, will diminish the powers of the microscope, and how often the instrument is blamed for indistinctness, when the real fault lies in the carelessness of the operator. Even when the greatest care is taken, dust is sure to settle on the glasses, especially on the eye-piece, and before using the microscope the glasses ought to be carefully examined. Never wipe them with an ordinary handkerchief, but get a piece of new wash-leather; beat it well until no dust issues from it, and then put it into a box, with a tightly-fitting cover. Use this, and nothing else, for cleaning the glasses, and you will avoid those horrid scratches with which the eye-glass and object-glass of careless operators are always disfigured.

Moisture is very apt to condense on the glasses and to ruin their clearness. If the microscope be brought from a cold into a warm room, the glasses will be instantly covered with moisture, just as the outside of a tumbler of cold water is always covered with fine dew when brought into a warm room. The microscope should therefore be kept at least an hour in the room wherein it is to be used, so that the instrument and the atmosphere may be of the same temperature. You should make the microscope a trifle warmer than the surrounding atmosphere, and so avoid all danger of condensation. When changing the object-glass or eye-piece, always keep the hand as far away from the glass as possible, and manipulate with the tip of the forefinger and thumb. The human skin always gives out so much exhalation, that even when the hand is cold the glasses will be dimmed; and it is a peculiarity of such moisture, that it adheres to the glasses with great pertinacity, and does not evaporate like the dew which is condensed from the atmosphere.

In order to insure perfect success in this important particular, the young microscopist will do well to get the optician from whom he purchased his instrument to explain its construction, and to give him a lesson or two in the art of taking it to pieces and putting it together again; for unless each glass can be separately cleaned, no one can be quite sure that the instrument will perform as it ought to do. The best method of ascertaining whether it is quite clean is to throw the light upwards by means of the mirror, and then to turn the eye-piece slowly round. If any dust or moisture has collected either upon the eye-glass or the “field-glass,” which forms the second lens of the eye-piece, it will be immediately detected. Turning the object-glass will in a similar manner detect impurities upon its surface.

We will now proceed to the manner in which objects are examined. Suppose, for example, that we take a buttercup-leaf, because it can be found at almost any time of the year. Place a piece of glass on the stage, lay the leaf on it, put on the lowest power, set the focus, and then look at the leaf. You will probably be disappointed, and see nothing but a confused mass of undulating dark green, like a green carpet thrown carelessly on the ground, and seen in the dim twilight.

Two points are now needed; the first being to get the leaf flat, so as to avoid the undulation, and the second being to throw a proper light upon it.

Take out the leaf, and, instead of laying it entire under the microscope, select the flattest part, and cut it out with scissors. A piece the size of a silver penny will be amply large enough. Lay this piece on the glass, get the focus afresh, and then look through the microscope. The leaf will now appear much more regular, and will be seen as a rough surface, mottled with white and traversed by pink and green ridges, which are the large and small nervures. By means of a mirror or the condenser throw a brighter light upon it, and it will be seen to be covered with a slight roughness, the nature of which cannot be clearly ascertained; then add the next highest power, and try if the structure of that roughness can be made out. Curiously enough, although the magnifying power has been more than doubled, the roughness has much the same appearance as before; so that we must try another plan, and look at the leaf edgeways.

Take the piece of leaf in the stage-forceps, but do not touch it with your hand; fix the forceps on the stage and turn the leaf so that it presents its edge to the object glass. Get your focus, and you will now see the cut edge of the leaf, and will at once distinguish its structure. On either side may be seen the upper and lower cuticle, and in the centre the soft green substance, or “parenchyma,” as it is called. From the cuticle project a number of short hairs, and when the focus is accurately obtained, the cause of the roughness will be seen in a vast number of minute projections, which are, in fact, identical in structure with the hairs, though not so well developed. The under-cuticle of the leaf is much more interesting than the upper.

Now change the illumination, and, instead of throwing the light upon the object from above, turn the mirror so as to direct it through the object from below. No apparent result will follow, because the leaf is so thick and opaque that the light cannot pass through it. Hold the leaf horizontally, and, by means of the stage-forceps, rip it smartly across, and if you do this rightly, you will find that the two cuticles are partly separated, so as to allow either to be examined separately. At first the leaf will most probably be torn along one of the large nervures, so that the cuticles are not perfectly separated. Never mind failure, but try again; and you are sure, after a few efforts, to hit upon the right method of tearing the leaf.

One of the most useful capabilities of the “live-box” is now shown. As may be seen by the [figure and section], it consists of an inner tube with a thick glass, and an outer tube with a thin glass. The outer tube can be taken off, water or any other substance laid on the thick glass, and then the outer tube or cover is slid down upon it until the object is pressed flatly between the two glasses. When you have succeeded in getting a convenient slip of the leaf, lay it on the thick glass of the inner tube, and put a drop of water on it. Put on the cover, and push it down until the piece of leaf is pressed flat, without being squeezed. Now look through the microscope, and you will see a beautiful sight, showing how much there is in a despised leaf, which we daily tread under foot.

The cells of which the cuticle is chiefly composed are seen in many a waving outline, while at their points of junction are placed the remarkable contrivances called “stomata,” or mouths, which are the apertures through which the atmosphere is enabled to penetrate into the interior of the leaf. The two semilunar cells at the sides of the opening may be considered as lips, which open and close according as the plant needs the air or not. The numerous dots which are seen upon the leaf are of a vivid green colour, and it is to their presence that the leaf owes its hue.

We have given these details because they are applicable to the examination of all leaves and petals, and show the young observer the method which is to be adopted when looking for the first time at a strange object.

If the microscopist should follow up his work properly, and make sketches of every object which he places under the microscope, he cannot do better than use the camera-lucida, a neat little instrument, which is fitted into the eye-piece of the microscope. Dr. Beale’s neutral glass is as efficacious in careful hands, and only costs a fourth of the sum. This instrument cannot be applied to the ten and twenty shilling microscopes, as it requires that the tube should be perfectly horizontal. The method of using it is simple enough.

After fixing the object and getting the right focus, set the instrument horizontally, and arrange the light so that the object is well illuminated, and its lines quite clear and well defined. Now remove the cap of the eye-piece, and fix the camera-lucida in its stead. Lay a drawing-pad on the table under the camera-lucida, look through the square opening (or, if you use Mr. Beale’s glass, look through the neutral glass), and you will see the object apparently projected on the paper. We say apparently, because in reality the image is not thrown on the paper at all, but on the camera, and the eye refers it to the paper, as being the nearest object. In fact, the principle on which this camera-lucida is arranged is exactly that of the Polytechnic ghost, which appears to be in one place, whereas it is in another.

Now take a pencil, cut it to a very fine point, and trace the outline of the object on the paper. At first you will think this to be an impracticable task, for the point of the pencil will totally vanish. Soon, however, the eye will so adjust itself as to see the pencil and the object perfectly well, and by a little practice the observer will be able to sketch every object as rapidly and firmly as if he were copying a drawing, by means of tracing-paper. The neutral glass is perhaps to be preferred to the camera-lucida, as it is learned more easily, and gives less trouble than that instrument. Its cost is five shillings.

After you have practised yourself well in the handling of the microscope, your ambition will take another step, and lead you to the preparation of permanent objects. In order to set yourself up with the needful apparatus, you will have to disburse about five shillings. A small spirit-lamp will cost eighteenpence, and a small bottle of Canada balsam, another of asphalte varnish, and another of Dean’s gelatine, will make about eighteenpence or two shillings more. A few pence will purchase a sheet or two of ornamental paper, and a few more a flat plate of brass or copper, about five inches by three. The rest of the five shillings may be expended in “slides” and thin glass, cut square.

Slides are merely slips of glass, three inches in length by one in width, and the thin glass is used for laying upon the objects and defending them from dust. We advise the square glass, because it scarcely costs one quarter as much as the round glass, and is equally effective when properly managed. There are several methods of “putting up” preparations—namely, dry, in Canada balsam, in gelatine, and in cells. We will take them in their order.

The simplest plan is, of course, the “dry” mode. Suppose that you want to preserve a tiny piece of down, or the scales from a butterfly’s wing. First wash all the slides and glasses well, by dipping them into a strong solution of soda, and then into hot water, in order to get rid of grease, taking care never to touch them with the hand, but to take them out of the water with the forceps. This can be done at any time, and the glasses carefully wrapped up and placed in a box ready for use.

You now select one of the slides, and lay the object exactly in its centre. If very minute objects are used, they must be examined in order to see whether they are properly disposed. The next process is, to take one of the thin glasses with the microscope, and lay it very carefully over the object. Then cut a piece of ornamental paper, about two inches long and seven-eighths of an inch in width; cut or punch a circular piece out of its centre, damp it well, and cover the wrong side slightly, but completely, with paste. Lay it on the slide, so that the centre of the hole shall coincide with that of the object, work it down neatly with the fingers, and it will hold the square piece of thin glass, which is technically called the “cover,” in its place. Watch it occasionally as it dries, and be ready to press down any part of the paper that may start up. Write, with ink, the name of the object on the end of the slide.

When you have made a dozen or two of these preparations, it will be time to letter and index them. On each slide paste a slip of white paper, and on the paper write a brief notice of the object, thus—

SCALES.
D. HEAD MOTH.

Then scratch with a bit of flint, or with a writing-diamond, if you have one, a number on the end of the slide, and have a note-book with a corresponding number opposite to which you enter the description at a fuller length, thus:—

18—Scales of Death’s Head Moth (Acherontia Atropos), from centre of
under-surface of right fore wing. Dry. June 4, 1864. +

The cross signifies that you prepared the object yourself, and the reason for adding the date is, that in after years you will have a valuable guide as to the durability of your preparations. If the specimen has been purchased or presented, always add the name of the seller or donor, as well as the date. These precautions may seem to be needlessly minute, but we have so often seen whole sets of valuable preparations rendered useless for want of ticketing, that we cannot too strongly impress on our readers the necessity for the note-book as well as the label, the one acting as a check upon the other. When the label has been affixed, and the details transferred to the note-book, the ink may be washed off the end of the slide.

There is another convenient method of putting up the elytra of beetles, parts of various insects, mosses, minute shells, and similar objects. Take a common pill-box of the smallest size, and cut a little cylinder of cork, that will nearly, but not quite, equal the height of the box, and fasten one end to the bottom of the box with glue. Now blacken the interior of the box and the cork cylinder. Put a little drop of Canada balsam, Arabian cement, or gum Arabic on the top of the cylinder; put the object on it, press it into its place, and, when the cement is hard, the preparation is complete. The cover of the box serves to keep the object from dust.

Now we come to the Canada balsam, a substance which produces beautiful effects when rightly handled, but is most aggravating to the learner, causing alternate irascibility and depression of spirits. Many objects, such as the antennæ and feet of insects, will not show their full beauty unless they are mounted in Canada balsam. The method of doing so is as follows:—A week or two beforehand put the objects into ether or spirits of turpentine, and allow them to remain there until wanted. Pile up some old books, or take a couple of convenient wooden blocks; lay your brass plate upon them; light the spirit-lamp, and put it under the plate so as to heat it. Lay two or three slides on the plate, and all then can be heated at the same time.

Warm the bottle of Canada balsam, and with a glass rod take out a very little drop, and put it exactly in the middle of the slide. In order to insure this point, I always put a dot of ink on the wrong side of the slide. Stir it about with one of the needles mentioned on [page 428], and if any bubbles rise, break them. When the balsam is quite soft and liquid, take one of the objects out of the bottle and put it into the balsam, exactly over the black dot. Now add a little more balsam, so as to cover it, and let it lie for a few moments. Take one of the glass covers, put a very little balsam on its centre, and lay it neatly over the object, pressing it down gradually and equally. Unless this be done, the object will not remain in the centre, but will shoot out on one side, and the whole operation must be begun de novo. Remove it from the hot plate and lay it on a cool surface, still continuing the pressure until the balsam has begun to harden. Lay a little leaden weight—a pistol-bullet partly flattened is excellent for the purpose—and on the cover write the name of the object, as already mentioned, and then proceed to prepare another slide.

Twenty such slides may be prepared in the course of a morning, and when they are finished they should be laid carefully in a cold place, where they will be free from dust. In a week or so the balsam will be quite hard, and then the slide may be completed. Take an old knife, which should be kept for this special purpose; heat the blade in the spirit-lamp, and then run it along the edges of the slide, so as to take off the superfluous balsam which has escaped from beneath the cover. This must be done very quickly, or the balsam inside the cover will be heated by the knife, and the preparation spoiled. When this is done, cut the ornamental paper, as already described, number and label the slide, wash off the ink, and then the preparation is complete. Some objects are very troublesome to prepare, and require to be soaked in turpentine and boiled repeatedly in the balsam before they are completely penetrated with it.

Objects which are put up in Deane’s gelatine are managed after a similar fashion, save that the gelatine is to be heated by placing the bottle in hot water, and that the turpentine is not needed. Vegetable structures show beautifully when thus prepared. To remove the superfluous gelatine use a wet and not a hot knife.

Cells are very difficult to manage, and the novice had better not attempt to make them, but is hereby advised to purchase them ready made. Suppose that the young microscopist has dissected the digestive organs of a bee, and wishes to preserve it in spirit; his best plan will be to use a cell for the purpose. Let him buy a cell of sufficient depth, float the preparation into it, fill it up with spirit, put the cover loosely on, and leave it for a week, occasionally raising the cover and stirring the preparation with a needle, in order to get rid of any air-bubbles that may have been entangled in the tissues.

Then let him wipe the edges of the cell very dry, put on a slight layer of gold-size or asphalte varnish—the former is preferable—fill up the cell a “bumper,” and lay the cover very gently upon it, beginning at one end and gently lowering it. With blotting-paper the liquid that escapes must be removed, the edges dried afresh, a flattened bullet placed on the cover, and with a very small camel’s-hair brush the slightest possible coating of size painted round the edge of the cell. When it has hardened another may be given, and so on, until a thick hard wall of size has been built up round the edges and made the cover completely air-tight.

We presume that the reader does not intend to use his microscope merely as a toy, but that he desires to gain some insight into the works of Nature, and is therefore willing to set to work in a systematic manner.

It is now known that both animal and vegetable structures are built up by means of certain minute particles, technically called CELLS, and that in every part of a plant or of an animal can be recognised the constituents of which it is formed. We will, therefore, begin with the vegetables.

CELL, STRAWBERRY.

Some of the lowest plants, such as the minute algæ that inhabit the water, afford excellent examples of the simple vegetable cell; but as these plants are not readily procured by a beginner, we will select some familiar object wherein the cells may be found. If any soft and pulpy fruit be taken when it is quite ripe, and submitted to the microscope, the vegetable cell will be seen in a tolerably perfect form. The three rounded objects shown in the accompanying [illustration] are cells from the strawberry, specimens of which can easily be seen, if a very thin slice be cut with a razor or lancet, the latter being the preferable instrument. Be careful to dip the blade in water before cutting the fruit, and to float the slice from the blade to the glass slide by placing them both under water. Unless this precaution be taken, the section will not be flat, but will be crumpled up, and the cells will not be properly seen.

Within each of these cells may be seen a small rounded object, which is technically called the “nucleus;” and in some cases a smaller nucleus, called the “nucleolus,” may be observed within the nucleus itself. The increase of cells mostly takes place by a process of division. A line passes across the nucleus, which presently separates into two distinct parts, each of which recedes from the other, causing the cell to enlarge and alter its shape. Presently a line is seen across the cell itself, and in due time the cell is also divided into two parts, each having its own nucleus.

In the present instance the cell is totally spherical, because the fruit from which it was taken was soft, and allowed the constituent cells to expand. When, however, the vegetable substance becomes hard, the cells are pressed closely together, and their shapes are very much altered. Sometimes, when the cells are of nearly the same size, and the pressure is equal on every side, the cells form regular twelve-sided figures, called “dodecahedra,” which, when that occurs, show a six-sided outline. A very thin slice of raw potato will show the twelve-sided cells beautifully, and has the further advantage of exhibiting the starch globules with which the cells are filled. Here is a [figure] of a potato cell, which presents a six-sided outline, just like that of a bee’s waxen dwelling, and which is crowded with the beautiful globules of starch. If the reader likes to make a few dozen balls of clay, and to squeeze them together in a mass, he will find that the central balls will have lost their globular shape, and assumed a more or less regular twelve-sided form, very much like that of the potato cells.

CELL, POTATO.

STELLATE TISSUE.

CELL, POTATO.

STELLATE TISSUE.

Sometimes the cells run out longitudinally into cylinders, and attain the really enormous length of three inches; sometimes they become flattened, as the skin or epidermis of many plants; and oftentimes they push out their sides into arms or rays, like stars, and form the tissue which is technically called “stellate.” [Here] is a specimen of stellate tissue taken from the pith of the common rush, wherein the rays are seen to be very regular: generally, however, the rays are extremely irregular, and require some little practice to detect them. Stellate tissue may be seen in the white portion of orange-peel, in the thick fleshy substance of many aquatic plants, in certain leaf-stalks, and in many similar objects.

We will now see how the soft cells which form the pulpy fruit of the strawberry can be changed into the hard timber of the oak or iron-wood tree.

RINGED STRUCTURE.

Wherever a cell is destined to form part of a permanent tissue, it is strengthened by receiving certain additions to its walls. These additions are technically known as “secondary deposit,” and are made in various ways. Sometimes they extend in a thin layer over the whole cell-wall, leaving a number of little holes, which are called “pits,” and earning the name of “pitted structures.” Very frequently the secondary deposit is arranged in a series of rings, an example of which is given in the accompanying [illustration]. This object is taken from the mistletoe. Good examples of the ringed structures may be seen in the anthers of many plants, and in the leaf-stem of the common rhubarb, an example of which is shown in the next [illustration]. Another very common form of secondary deposit is the spiral, which is generally used where strength and elasticity are united. Two examples of the spiral form are given in the [illustration]; the first taken from the lily, and the second from the “rhizome,” or subterranean stem of the water-lily.

RINGED AND SPIRAL STRUCTURES.

Another beautiful form of secondary deposit is seen in the fern root. If the root be cut longitudinally, and the dark hard fibre dissolved carefully out with nitric acid, the deposit will seem to have assumed the shape of a winding staircase, and is then called “scalariform,” or ladder-shaped. Similar structures may be found in asparagus.

WOOD-CELLS.

The reader will see that the hardness of the structure depends entirely on the amount of secondary deposit, and we accordingly find that when the wood is hard and fit to be worked with tools the cells are almost wholly filled with the secondary deposit. In this state they are called “wood-cells.” Examples of these cells may be seen in the accompanying [illustration]. In the first example, which is taken from the elder-tree, four cells are shown in order to display the manner in which their pointed ends are arranged. (The reader must remember that in all wood-cells the ends are pointed.) In the next example, which is taken from the chrysanthemum, the pitted structure is still retained; but in the last figure, which is drawn from the lime-tree, the entire cell is filled with secondary structure. The reader must understand that we can only give the veriest outline of the subject, and profess to do nothing more than indicate the method of observation, leaving the pupil to work out the details by himself.

HAIR OF LAVENDER.

Another curious development of the plant-cells is the formation of HAIRS. These objects alone afford an inexhaustible field for the microscopist, and any one who chooses to work out the subject will find himself repaid if he makes a good series of preparations. In their primary forms the hairs are seen merely as little projections on the epidermis, whether of the stem, leaf, or petal, and by degrees assume their varied and beautiful forms. In order to show the singular forms which hairs sometimes assume, an [illustration] is here given of the hairs of the lavender leaf. This is one of the hairs that give the leaf its silvery gloss. It consists of an upright stem, from the top of which a number of forked branches shoot out horizontally, much like an open umbrella held upright. The object of this remarkable form is, that the delicate vessels in which the perfume is held should escape injury. If the reader will refer to the second figure, which represents a much magnified view of the edge of the leaf, he will see the globular perfume-gland standing under the shelter of the branching hairs.

The following plants afford valuable examples of hair:—Arabis, marvel of Peru, sowthistle, tobacco, southernwood, hollyhock, snapdragon, pansy (in throat of flower), deutzia (under-side of leaf), verbena, alyssum, tradescantia, borage, cowhage, and many others. The beautiful effect produced by the petals of flowers is caused by the imperfect hairs with which their surfaces are studded.

The POLLEN of plants is always worth observing, and some specimens are of remarkably beautiful shapes. Take that of althæa, crocus, cactus, heath, violet, daisy, lily, snowdrop, wallflower, willow-herb (a very beautiful form), hollyhock, periwinkle, primrose, &c. Put some up in Deane’s gelatine, and dry some, besides examining them all when fresh.

The microscopist ought to examine the structures of WOOD by making sections in the directions transverse and longitudinal. A razor will answer very well for the purpose, and the wood should always be soaked inside, and the razor wetted before the section is made. It is often useful to make diagonal sections of several woods, especially those of the pine and juniper. All the forest trees should be examined, and their roots and bark should not be omitted. Cut sections of coconut-shell, vegetable ivory, sugar-cane (a most beautiful object when mounted opaque), bamboo, butcher’s broom, &c.

Mosses are beautiful objects, and can always be found. Examine particularly the fruit or seed-vessel, and note the structure of its different parts. Put these on a slide, and breathe on them, noting at the same time any change which may take place.

The SPORE CASES of ferns are extremely beautiful, and should be carefully examined. The little brown dots or streaks that are seen on the under surface of the fronds are called “sori,” and contain a large but variable number of the sporanges. These consist of stalked sacs or cases, and differ much in shape, according to the species of fern. If the fern be fresh from which the sorus is taken, the sporanges may be seen writhing and twisting like so many serpents, and sometimes it happens that one of the sporanges bursts, and suddenly covers the field of the microscope with minute black dots. These dots are the spores or seeds of the fern, and when magnified with a very high power, they are seen to be variously shaped. One of the most remarkable spores is that of the equisetum, or mare’s tail of the water. This spore looks like a ball with something coiled round it. As soon as the spore is discharged from its case, four threads are seen to uncoil themselves from around it, and by their elasticity to cause the spore to jump about as if alive. These fibres are technically named elasters, and are prolongations of the outer coat of the spore.

Fungi of all kinds should be examined. There is never any difficulty in finding fungi, though the autumn is the best time of year for this purpose. “Mould,” as it is popularly called, is a form assumed by many species of fungus, which, though objectionable to the careful housewife, are full of interest to the microscopist. The well-known mushroom and toadstools are the highest of the fungi. The black spots on leaves are fungi, mostly belonging to the genus puccinia, and the best specimens are generally found on the wild rose or bramble. The black “smut” of wheat is another fungus, very pretty under the microscope, but very obnoxious to the farmer; and the “bunt” also belongs to the same vast tribe of plants, four thousand species of which are now known to exist.

The young observer should also look for the beautiful crystals which exist in many vegetable cells. The RAPHIDES, as these crystals are called, are of various forms, mostly shaped like curved needles, but often assuming very pretty and regular outlines. Raphides are plentifully found in the bulb of the onion, in the rhubarb, the lily, the iris, &c. They are best mounted as opaque objects and, if the reader can procure a binocular microscope, he will see the form of the raphides better than with the single-tube instrument.

Seeds of different plants should be carefully examined, especially those of small dimensions, which often exhibit some wonderful beauties of structure. The winged seed of various plants, such as the thistle, the dandelion, the valerian, and the willow-herb, are extremely interesting objects; while those of the yellow snapdragon, the mullein, the Robin Hood, and the bur-seed, are remarkably beautiful in form, though they have no parachute, as the feathery appendage is called.

Leaving dry land, we will devote a short time to the water. Let the reader take with him the simple collecting apparatus mentioned on [page 430], and secure specimens of the water from different ponds, ditches, and streams. For collecting the larger objects a little net, which can be purchased cheap, is of very great use. It is easily made by any tinman, and if the young microscopist knows the use of solder, as all experimental philosophers ought to do, he can put it together in a few minutes. It is formed of a strip of zinc bent into the requisite form, and with a socket, to which a handle can be attached. A piece of coarse muslin, or, rather, fine “net,” is then stretched over the bottom, and the apparatus is complete.

In the water is sure to be found one of the lowest forms of vegetable life—namely, the “confervoid algæ.” Look for these in bright, clear pools, placing the collecting bottle near any greenish film collected around the stems of plants, or spread over the stones on the bed of the pool. If this film be very carefully taken up, it will produce many interesting forms of vegetable life. One of the most remarkable of these vegetables is that which is called “volvox globator,” a figure of which is [here] given.

VOLVOX.

This wonderful object is about as large as the head of a very small pin, so that it is visible to the naked eye, and looks like a tiny globule passing through the water. When it is placed under a lens of moderate power, say of an inch focus, it exhibits some very strange peculiarities. It continually revolves, and by its revolution is able to enjoy a moderate degree of locomotion, though without any apparent object. Small dark spots are also seen upon it.

If a half-inch lens be now used, the structure of the volvox begins to be exhibited. The whole surface is covered with a network of very fine fibres, having a spot at the intersection of each mesh. On applying a still higher power, say the four-tenths of an inch, the structure is further elucidated, and the dots on the surface are seen to consist of greenish bodies, each furnished with a pair of delicate fibres, technically named cilia, which are constantly vibrating, and cause the revolution of the general mass. The dark spots are now seen to be the young plants in different stages of progress. From six to ten of these are inclosed within the parent, and when the latter has reached its full age, the membrane bursts asunder, and the little volvoces are liberated.

CLOSTERIUM.

Another interesting form is the closterium, a genus which is sure to produce several good examples. We may mention that the ponds in Blackheath are very rich in these curious vegetables, and a very considerable series of confervoids may be obtained from them. The closteria are easily recognised by their resemblance to the Australian “boomerang.”

As our space is rapidly waning, we must leave the vegetable, and proceed to the animal kingdom.

As is the case with vegetables, the animal structure is composed of cells, though they cannot be so easily traced as in the examples which we have already noticed. The young observer may readily perceive the animal cell, in its largest and simplest form, by placing a little of the yolk of egg under the microscope. CARTILAGE, or gristle, is easily seen to be composed of cells. The nails of the fingers afford good objects for the microscopist in search of animal cells. If a thin section be placed under the microscope, none but an experienced observer will be able to make out the presence of cells at all; but if the section be soaked in “liquor potassæ,” the cells immediately swell up, and their shape is at once made plain. Take the BONE of a young chicken or rabbit, and make a thin section that embraces both the bone and cartilage, and there will then be a beautiful object for the microscopist, showing how the cartilage is changed by degrees into bone.

BONE, TRANSVERSE.

Sections of bone should also be made, both transverse and longitudinal.

The BLOOD is another object which must be carefully examined. The “corpuscles” which give the colouring matter to the blood are cells of different size, according to the creature from which they are taken. The dimensions of the animal exercise no apparent influence on the corpuscles, for those of “proteus anguinus,” a little creature not larger than a lamprey, are many times larger than those of the ox. In the accompanying [illustration] is shown a series of specimens, in order to show the great difference in their shape and size, all being drawn to scale and magnified by the same lens. The circular corpuscles in the left-hand upper corner are those of man; immediately below is a single corpuscle from the pigeon. The great central corpuscle is taken from the proteus; the two in the lower right-hand corner are from the frog, one of these being viewed edgeways; and of the remaining two, that on the left hand belongs to the tortoise, and that on the right to a fish.

BLOOD CORPUSCLES.

The insect tribes are an inexhaustible source of objects for the microscopist, who may find that even a single fly will give him employment for many months. The scales from the butterfly’s wing, the wonderful compound eyes with which insects are gifted, the structure of their feet, and their entire anatomy, are always at the service of any microscopist who really cares for his work. It would, of course, be impossible to give even a list of the interesting portions of the different insects; so one or two examples must suffice us.

ANTENNÆ OF FLY.

Take the ANTENNÆ of the insect tribes, and see how beautifully they are formed, how graceful is the shape, and how elaborate the structure. A low power will be useful for exhibiting their general shape and outline, but it is not until we know how to use the higher powers that the real beauty of these curious organs is seen. In the accompanying [illustration] is given part of an antenna of the common blue-bottle fly, in order to show the remarkable cavities which exist within the antennæ, and which are thought by some anatomists to be organs of hearing, and by others to be organs of smell.

WINGS OF BEE.

The WINGS of insects are also most remarkable, and possess many peculiarities of structure which cannot be detected without the aid of a microscope. Take, for example, the wings of any hymenopterous insect, say those of a humble-bee, and see how beautiful is the structure which causes the four wings to be united into two when the insect is about to fly. In the [illustration] may be seen a pair of these wings, together with the row of hooks which bind them together. A still more magnified representation of the hooks is placed near the wings.

It is now ascertained that the wings of insects are connected with the breathing apparatus, and that the respiration of the insect extends even to the very tips of these singular organs, which are not modifications of existing limbs, as in the birds, but additional structures. The circulation of insects may often be seen by placing a portion of a transparent wing under a moderately high power. We have often seen it in the wing of the great water-beetle. A series of very beautiful preparations may be made in order to show the distinction between the wings of different insects; and as the orders of insects are founded upon their wings, there ought to be at least one example of each order. The proboscis of insects is always worthy of careful examination.

As to the breathing apparatus itself, the best mode of examining it is to open a caterpillar, remove a part of the large breathing tube which runs along each side, and place it under the microscope. It should always be taken so as to include one of the spiracles, or breathing-holes. An example of a breathing-tube, taken from a silk-worm, is given in the [illustration].

BREATHING-TUBE, SILKWORM.

Hairs of animals are very curious and interesting objects. They should be mounted in three modes—namely, dry transparent, dry opaque, and in Canada balsam, transparent. Be sure to procure some hair of the bat, the sheep, the mouse, the deer, the mole, and any of the weasel tribe. Many insects have very beautiful hair, but the most lovely hair in the animal kingdom is that which is obtained from the sea-mouse. Fish scales should also be procured, and specimens should be taken from the lateral line.

Molluscs of all kinds afford many beautiful objects, and the observer should be very careful to examine the wonderful tongue-ribbon of the snail, the slug, the periwinkle, the whelk, and other similar molluscs. If meant to be examined by polarized light, the tongue-ribbon should be mounted in Canada balsam.

Crystals should always form part of a collection. Take those of common salt, nitre, sugar, chlorate of potash, salicine, &c.; indeed, anything that will crystallize should be prepared and mounted, as such objects will often be most useful when examining unknown substances.

BIRD’S-HEAD PROCESS.	NOCTILUCA.	PEDICILLARIÆ.

BIRD’S-HEAD PROCESS.

NOCTILUCA.

PEDICILLARIÆ.

Zoophytes must of course find a place in the cabinet, and the young microscopist ought to put up a few specimens of the “bird’s-head” processes which are found in the bugularia and other inhabitants of the sea. The pretty noctiluca, to which is mostly owing the phosphorescence of the sea, should be preserved, and the extraordinary appendages to the skin of certain star-fish and sea urchins should be examined. These are called pedicillariæ, and a sketch of them is given in the [illustration].

---