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.
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
center 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 New York, the whole of Philadelphia, 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 day 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. It 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 dollar or so, 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 in water, together
with the glass, and watch carefully the sub-aquatic 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 practiced microscopists, and those who are possessors of the
most elaborate instruments, are the very men who are the most certain
to have a pocket-lens about them, and to use it most frequently.
Practice well with the pocket-lens before you meddle with the compound
microscope. You will waste no time, but will rapidly gain by it; for
you will be learning the rudiments of a new science, and laying a solid
foundation on which to build.
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 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 favor, and with others the left; and when the favorite
eye gets all the work, it too frequently suffers. Whether you look with
the right or the left eye, _keep both eyes open_.
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 piano-forte 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 a 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.
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.
Melt three or four pounds of lead in an iron ladle, and make a mold,
consisting of a hollow hemisphere of paper or cardboard, through the
center 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 mold 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. 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.
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 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.
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. 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 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 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 favorable.
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,
then cut it away longitudinally, so that a long tongue of gutta-percha
is left, 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 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 a 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 unskillful operator is apt to press the sides
unequally, and to leave a bulging projection at the end.