made the experiment. Nor is this the
occupation of a trifler; for, while thus occupying
our leisure, we unconsciously attain a
comprehensive view of the Great Artificer's
wisdom and power.

Microscopic preparations are fast increasing
in importance, as an article of commerce; they
are one of the many battle-grounds of competing
rivalries. Rich men, as amateurs, and men
of science, as students, form with these their
microscopic museums, as others keep their
microscopic menageries. Collections and
cabinets of microscopic preparations are to
be purchased, containing from a dozen to a
thousand objects and upwards; and lists and
catalogues are published from which the
buyer may choose the articles that best suit
his taste or illustrate his studies. With the
aid of these preparations, there is no reason
why the microscope should not become an
instrument of drawing-room recreation, quite
as much as the stereoscope, over which it has
the advantage of variety, to speak of nothing
farther or higher. For, although the portraits
of microscopic objects, drawn and engraved
and coloured after life, are often very
beautiful and wonderful performances, and a
volume of them will help you to spend an
interesting evening, still they are faint
and feeble nothings when compared with the
objects themselves as seen under a good
instrument. Their great utility lies in their
helping you to recognise the originals
themselves, when you meet with them. With the
solar or oxyhydrogen microscopes exhibited
at public lectures, you only see the shadow of
the thing displayed; but, with a good
compound microscope you behold the thing itself
actually and bodily.

The ordinary routine of manipulation for
the production of good preparations will be
found in most elementary treatises on the
microscope; in Carpenter, Queckett, Hogg,
Beale, and others. Nevertheless, I will give
a few supplemental hints, kindly communicated
by an expert practitioner, which may
be useful to the student, and even to those
who are more advanced.

In mounting in balsam, if your object be an
animal preparation or any other liable to curl
under the influence of heat, first evaporate
your balsam on the slide to such a consistence
that it will harden readily on cooling; take
it from the source of heat, suffer it nearly to
cool, then place on it your object, and then,
upon the object, your glass cover. Heat it
again slowly. The heat, equalised by the
cover, prevents the curling, and the preparation
is mounted in the usual way without
further difficulty.

In mounting animal preparations in balsam
—or others which from circumstances
require moistening first with turpentine, as
fern-sporules, foraminifera, and such like—let
the balsam be afterwards heated very, very
gradually. By this you avoid bubbles, and
evaporate the turpentine completely, so as to
make a finer and clearer preparation. The
sooner balsam preparations are cleaned after
being mounted, the easier it is to do it.

In preparing diatomaceæ,* either fresh or
from fossil earth, there is but one mode of
procuring good specimens. Wash your earth
thoroughly. Having prepared five or six
clean cups, pour it from one to the other,
allowing it to stand one minute in the first,
two minutes in the second, four in the third,
eight in the fourth, and so on in similar
proportions. Try them all under the microscope,
and you will find that probably only
one will yield good specimens.
* See Household Words, vol. xiv., pages 293 and 294.

All saline solutions, being slow of evaporation,
are easier to mount in than spirit. The
only art of mounting in flat cells consists in
the drying of each coat of varnish (gold-size
is the best) before the next is applied. In
wet weather, three days should elapse between
the first and second coats; in dry weather,
one is enough. When the second coat is
on, the preparation is for the time safe; the
third and fourth may be applied at longer
intervals. Some few out of a series of
cell-preparations will always spoil; but, by
adopting this precaution, our experienced
practitioner has been successful in a hundred
and forty-eight out of a hundred and fifty
preparations, over and over again.

Dry preparations, apparently so easy,
puzzle beginners most. There is a simple
way of mounting them; make previously a
sort of cup on the glass slides you keep in
store with a ring of gold-size painted on them.
The longer they are afterwards kept in store,
the better. When wanted for use, place on
them your object; slightly heat your cleaned
cover; drop it on the circle of gold-size;
press it down, and the preparation is finished.
If not thoroughly and completely dry, the
size will run. Difficult scales for test-objects,
as those of the lepisma and the poduræ, are
(I, the writer, think) better mounted dry
than in balsam.

Most infusorial animalcules, as soon as the
water in which they swim is evaporated,
tumble to pieces, or burst, even "going off"
gradually and regularly, as a Catherine-wheel
discharges its fireworks. No conservative
fluid keeps them well enough to allow them
satisfactorily to be offered for sale; for
private examination and use, five grains of
rock-salt, and a grain of alum, to the ounce of
undistilled water, answer best.

It will be seen from these brief practical
suggestions, that the preparer's art is no
mere mechanical routine. He must have
science to know what is worth preserving,
taste to arrange it gracefully and accurately,
and skill so to embalm his object as to retain
its beauty for future admirers. He must
have an artistic eye, a fine touch, an extensive
knowledge of Nature's minutiæ, and a
hand practised in the manipulation of his