350 
Fig. 167. 
Superior Compound Microscope. 
A A, base; B, pillar with joint at the top; CC, 
stem, containing square tube D, which is moved 
by a fine screw turned by the nut E; within this 
tube slides the square bar F, carrying the arm G; 
into this isscrewed the tube H, within which the 
compound body slides; I, the objective; K, 
stage-fork ; L, sprung tube, tightened by the nat 
N, carrying the frame of the mirror M. 
attributed to the fact, that, when the instrument 
is much inclined, the hinder foot receives 
nearly the whole weight, and the portions of 
the mstrument on the two sides so nearly 
counterpoise each other, that a very slight cause 
will communicate an oscillation to the whole. 
We can strongly recommend to our readers a 
basis of this kind, having not only our own ex- 
peeeee of its benefit to guide us, but that of 
iends whom we have induced to adopt it, and 
whose previously unsteady microscopes have 
been greatly improved thereby. It certainly 
does not possess the merit of portability ; but 
this, in a large microscope for observations of 
the highest kind, ought not to be a considera- 
tion. Nothing is easier than to have a separate 
tripod of the ordinary kind for use when occa- 
sion requires. To such a tripod Mr. Ross* 
has recently applied a method of construction, 
which he states to be very effectual in obviating 
vibration; but we cannot speak from experi- 
ence in regard to its use; and being well satis- 
* Microscopic Journal, No. 2. 
MICROSCOPE. 
fied with our own much simpler and less ex- 
pensive plan, we do not see the necessity for it: 
The pillar is just an inch in diameter, and 
consists of a stout brass tube loaded with lead. 
On the firmness of this part much depends. 
It is 8 inches from the foot to the centre of the 
joint. The middle piece of the joint is th of an 
inch thick ; and to this is attached a tubular 
clamp with a binding screw, which closely em- 
braces the stem. This mode of construction 
we adopted in accordance with the recommen- 
dation of Dr. Goring and Mr. Pritchard ;* but 
we are doubtful if its advantages counterba- 
lance the disadvantage of a certain want of 
fixity which it imparts to the remainder of the 
instrument supported by it. The stem is a 
thick brass tube of about f,ths of an inch in 
diameter ; to the upper part of it is firmly at- 
tached the stage, which is composed of a simple 
plate of well-hammered brass, 4 of an inch 
thick ; its length from the front of the pillar is 
4 a its breadth 24 orig aa “re domes 
ter of its aperture 14 inch. e only —_ 
preg. eitached to it is Ne fork, of whi 
e two wires work through sockets projecting 
from the under side of the stage. This fork is 
made sufficiently thin to poo a certain de- 
gree of elasticity; and, being firmly held in 
any position by the friction of its wires, it is a 
very useful means of holding aquatic boxes, 
slips of glass, large sliders, &c., affording, by 
its wide opening, (2 inches,) considerable free~ 
_ dom of movement to the object. The utility 
of this fork will depend upon the goodness of 
its construction in the first instance; it ought 
to work easily, and yet hold tightly in any po-~ 
sition. The sockets through which its wires 
pass should be sprung, so that they may be 
tightened at pleasure, should they work loose. 
The stage has a slight rim projecting into the 
lower side of the aperture, in order to hold 
various fittings which are attached to it by a 
bayonet catch, and holes are drilled in various 
parts of the stage (the massiveness of which 
prevents its being weakened thereby) for the 
reception of the pins of the forceps, condenser, 
&e. The stem carries a sprung tube, to which 
the mirror is attached, in the manner to be 
presently noticed. 
From the top of the stem projects a square 
tube, a little more than {,ths of an inch each way, 
the upper end of which is sprung, so as to 
grasp with sufficient firmness a solid bar of half 
aninch square, which slides up and down within 
it. The upper end of this bar carries the arm 
to which the body of the microsco 
on the accuracy of its formation the truth of 
movement will of course depend ; but if well 
made, a rise and fall of 34 inches may be 
allowed to it, without the slightest alteration in 
the position of the axis of the body which it — 
carries. The advantages of this sli in 
ment over the rack commonly employed for the 
coarse adjustment we as considerable ; 
very much time is saved ; for the arm may be 
shifted from its greatest to its least distance 
from the stage, in scarcely more time than is 
* Op. cit. 
is attached; _ 
‘ 
alls tie a 1 
