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SUMMARY OF CURRENT RESEARCHES RELATING TO 
is clamped in place by a strong tbumb-screw with milled head. From 
the back of the collar opposite the stage a strong screw projects, upon 
which a handle may be screwed when the instrument is to be passed 
about as a class Microscope. 
The arm is in two parts joined by a smoothly fitted joint with a nut 
on the pivot; the outer joint of the arm carries a slip-tube through 
which the body-tube is focused by sliding, and the inner joint of the 
arm is extended into a sleeve with a long conical bearing around the 
top of the pillar, insuring a smooth motion. A flat slotted plate is 
pivoted to the outer joint of the arm and rests on top of the sleeve of 
the inner joint, the top of the pillar passing through the slot, being 
threaded and pivoted with a strong thumb-nut to clamp the arm rigidly 
in place. By this construction the body-tube may be moved about over 
every part of a surface 6 in. square, and may be clamped in place over 
any part of that surface by means of the thumb-nut at the top of the 
pillar. The paper to be examined can be arranged on the large stage 
and secured in place by wire clips. In case it is desired to use the 
instrument as a class Microscope, the arm is clamped fast, the handle 
screwed on and the pillar unscrewed from the base-plate, when the 
instrument can be handed about as readily as a common stereoscope, and 
weighing but little more. 
If provision is required for the use of transmitted light, which is 
but seldom needed, an opening in the stage is provided, and a mirror on 
the base like that of a dissecting Microscope. An arm for carrying a 
lamp may also be attached to the pillar by means of a clamping collar 
like that of the stage-arm, when the instrument is to be used as a class 
Microscope at night. 
It has not been found requisite to provide for inclining the instru- 
ment in use, but if desired it can be readily accomplished by pro- 
viding a slotted segment on the plate into which the pillar screws, 
hinging this plate to an under plate secured to the base-board, with a 
clamp screw to clamp the segment against a projection on the fixed plate. 
The instrument, as made for me by the Bausch and Lomb Optical 
Company, has proved very satisfactory in use, and admirably serves the 
purposes for which it was designed, especially in its capability of being 
passed from hand to hand. An entirely unpremeditated advantage has 
also been discovered in the ease with which objects too bulky for 
examination on ordinary stands, such as large minerals, natural history 
specimens, &c., can be laid on the base-board 
(the stage being loosened and swung round 
out of the way), and examined with this Micro- 
scope over all their surface.” 
Magnifying Instrument.* * — M. Th. Simon, 
of Paris, has devised an instrument to replace 
the ordinary magnifying glass. It possesses 
the advantage of affording a well-illuminated 
image. The magnification is obtained by 
means of a concave mirror B. This is set at such an angle to a second 
mirror A, that the magnified image is formed in a convenient position 
* Zeitsclir. f. Instmmrntenk., x. (1890) p. 151. 
Fig. 47. 
& 
B x' 
