180 
THE MICROSCOPE. 
[Nature and Art, June 1, 1867. 
covered with the horns of the various animals of 
the country. This seems to have been a very 
ancient practice. There were horns on the altar 
of the Tabernacle, and Callimachus, in his hymn 
to Apollo, describes a similar mode of constructing 
an altar : 
“ Each day Diana furnished from her toils 
The horns of Cynthian goats, her sylvan spoils ; 
These did the god with wondrous art dispose, 
And from his forming hand an altar rose : 
With horns the strong foundations closely laid, 
And round with horns the perfect structure made.” 
(Dr. Dodd’s Translation.) 
THE MICROSCOPE. 
I N our last number we gave a short outlinear 
JL sketch of the progress recently made in the 
application of the microscope to the arts and sci- 
ences, and of the advance made in histological 
discovery. In the present article we propose to 
notice some of the more remarkable improvements 
and inventions in microscopic apparatus and appli- 
ances which have of late been described in the 
pages of our scientific contemporaries. In doing 
this we shall divide our subject into four or five 
distinct sections, which, if more or less artificial 
as divisions, are still useful for the purpose of 
description. All who are familiar with the com- 
pound microscope are aware that it consists of three 
separate parts — the tube or body containing the 
object-glass and eye-piece, which together constitute 
the magnifying apparatus ; the stage, or plate of 
brass, upon which the object intended for examina- 
tion is placed ; and the mirror, which, for ordinary 
purposes, is concave, and reflects through the object 
the light which falls upon it either from the sun or 
from some other source of light, such as a lamp. 
So much, then, for the general plan of the instru- 
ment. Supposing now it be desired to examine an 
object, it is obvious that the object must be found, 
and when found must be suitably mounted on a 
piece of glass before it can be placed upon the 
microscope stage for investigation. These pre- 
liminary remarks, then, show that our subject 
ranks itself under four distinct heads— (1) that of 
the microscope itself : its recently constructed 
varieties ; (2) the collection of objects ; (3) the 
mounting of the objects ; and (4) the illumination 
of the objects. Now under these different divisions 
we shall proceed to discuss the merits of some of 
the important appliances which have recently been 
invented by microscopists. First, of the micro- 
scopes themselves. Two forms of the microscope 
are now in very general use — the instrument with 
the single barrel, technically styled the uniocular, 
and that in which there is a tube for each eye — the 
binocular. It would take us too long to go into 
the principles of stereoscopic vision upon which the 
latter of these two microscopes depends ; but we 
may mention generally that the advantage of the 
binocular over the uniocular consists in the fact 
that it gives the eye a representation of the object 
in solid relief, whilst the uniocular gives merely a 
flat picture. The appearance of solidity given by 
the former being, in great part, due to the circum- 
stance that both eyes are employed simultaneously 
in viewing the object. Until quite recently, how- 
ever, the binocular was little better than an inter- 
esting toy, for it was impossible to employ it with 
any but the very lowest powers ; but since the 
application by Messrs. Powell and Lealand of an 
ingenious modification of Mr. W enliam’s binocular 
prism, the binocular can be used with the very 
highest powers. We ourselves have examined an 
object with the binocular microscope with as high 
a power as the 1-1 6th of an inch, by the assistance 
of the contrivance alluded to. The great difficulty 
which Messrs. Powell and Lealand had to overcome 
was that of obtaining an image by the whole aper- 
ture of the object-glass in each tube of the instru- 
ment. This, however, they effected (fig. 1) by 
interposing an inclined disc 
of glass with parallel sides, 
so that one set of rays from 
the object is transmitted 
directly through it to one 
eye, while the other portion 
of the rays is twice reflected, 
and thus sent along the 
second tube to the other eye. 
It is unnecessary to enter 
into further details here, as the figure will suf- 
ficiently explain the modus operandi of this 
ingenious appliance. 
Of binocular microscopes for both students and 
amateurs the best and cheapest is that which has 
been made by Mr. Collins, of Titchfield Street, for 
Professor Harley, of University College(fig. 2). This 
is a fine and solid instrument, and is characterized 
by a piece of apparatus which saves the observer a 
great deal of trouble and inconvenience. Instead 
of the simple drawer containing the prism, Mr. 
Collins employs an oblong box, one portion of 
which contains the prism and another a part of the 
polariscope. The second part of the polariscope 
lies beneath the stage, so that it can at once be 
brought into play. The advantage which this 
addition gives Mr. Collins’ instrument is this, that 
without any loss of time an object may successively 
be examined binocularly, uniocularly, and with the 
polariscope. Another convenient accessory to this 
microscope is the sliding bar upon which the two ob- 
jetives, 1-inch and -j-inch, are placed. By simply 
moving them either to the front or back a low power 
is substituted for a much higher one, or vice versd. 
A new class of microscope has recently made its 
appearance under the various titles of sea-side 
