26 
MECHANICAL PORTION OF THE MICROSCOPE. 
is inclined. A fine screw, with a milled head, at the right of 
the stage, gives a fine adjustment to the focus. 
Below the stage is a diaphragm plate, with orifices of differ- 
ent sizes to regulate the illumination, and a space between the 
largest and smallest orifices to exclude all the light, and give a 
dark background for viewing opaque objects. 
A concave mirror an inch and a half in diameter, suspended 
by a cradle joint, and movable in every direction, is used for 
illuminating the object. The mirror is so attached to the axis 
of the instrument, by a movable arm, that it can be turned so 
as to give very oblique light. 
This instrument is generally supplied with two eye-pieces, 
and with one’ inch and one quarter inch objectives of second 
quality, giving four magnifying powers, varying from 40 to 
350 diameters. 
This microscope is designed, as its name implies, for educa- 
tional purposes, for schools, private families, and for young 
people generall3^ Farmers, mechanics and merchants, who 
desire to devote some of their leisure hours to intellectual im- 
provement, or to the investigation of those branches of natural 
science more or less connected with their several avocations, 
will find this at once a cheap, substantial and efiicient micro- 
scope. 
As it is very steady and delicate in its adjustments, and can 
be used with the higher powers, the man of science will often 
find it a convenient substitute for the larger microscopes, when 
a more portable instrument is required for special purposes. 
46. The Students Microscope, shown in figure 8, is mounted 
on a firm tripod base, with uprights of japanned cast-iron, and 
moves freely on trunnions, so that it may be inclined at any 
angle. It has a plain stage three by four inches, furnished 
with spring clips, which retain the object on the stage when 
the instrument is inclined, and yet allow it to be ynoved freely 
in any direction. Plane and concave mirrors are set in the 
same frame, and can be rotated in any direction, or moved up- 
ward and downward on a sliding support. The adjustment o 
J. & W. GRUNOW & GO’S ILLUSTRATED 
