Every Boy's Book: A Complete Encyclopaedia of Sports and Amusements Part 66

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 bra.s.s cups, having gla.s.ses in them, which magnified slightly but defined clearly, or a great composition of bra.s.s and iron, looking like a rocket-tube, with an eye-piece at one end and a gla.s.s 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 s.h.i.+llings, 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 gla.s.s 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 gla.s.s, 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-gla.s.s, 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 ill.u.s.trate 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 circ.u.mstances 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 const.i.tuent 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.

[Ill.u.s.tration]

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 cla.s.s under the honoured t.i.tle 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 pa.s.sed. 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 ill.u.s.tration. Next take a piece of stout bra.s.s 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.

[Ill.u.s.tration: 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-gla.s.ses that are sold for a penny, and put it under the stand.

Lay a flat piece of gla.s.s 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-gla.s.s in a cork frame, and making it swing on pivots, like the gla.s.ses 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 gla.s.s. In many cases, a still neater manipulation is required,--as, for example, when the petals of flowers are under examination. Thin gla.s.s 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 gla.s.s plate, place a piece of the thin gla.s.s 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 gla.s.s, 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.

[Ill.u.s.tration]

These should be made of steel; but the young microscopist will find that a second pair made of bra.s.s, 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 fas.h.i.+on, 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-sh.e.l.l 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.

[Ill.u.s.tration]

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 ill.u.s.tration, as they would otherwise be too springy, and apt to tear the object instead of pulling or pus.h.i.+ng 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 s.p.a.ce 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.

[Ill.u.s.tration]

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

We take one of the old-fas.h.i.+oned 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 gla.s.s 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 ill.u.s.tration 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 gla.s.s 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 gla.s.s. 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 animalculae, 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 fis.h.i.+ng-rods without the top joint, as it can be carried without attracting attention, and can be lengthened at will by adding the different joints.

[Ill.u.s.tration]

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 acc.u.mulate in a kind of sc.u.m 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 sh.e.l.ls repeatedly during their lives, some species performing this operation every two days, a beautiful series of objects can be obtained by gathering the cast sh.e.l.ls, and preparing them for the microscope, according to the directions that will be found in the following pages. These sh.e.l.ls 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 r.e.t.a.r.d or hasten the change of sh.e.l.l, heat and light aiding development, and cold and darkness r.e.t.a.r.ding 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 a.s.sistance 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.