436 
SUMMARY OP CURRENT RESEARCHES RELATING TO 
from the object and the drawing-paper respectively. This object is 
usually accomplished by inserting between the drawing-paper and the 
eye a glass having the correct neutral tint. It is usually found that 
the exact tint required cannot be obtained, either because the properly 
tinted glass has been lost or broken, or never existed. In any case, 
such glasses are in the way, and can only have been regarded as a 
necessary evil. In the system here described, the light coming through 
the Microscope is first graduated so as to be as perfect as possible, then 
the diamond-shaped opening h is set so as to exactly equalise the lights 
coming from the Microscope and from the drawing-paper located on the 
circle under the pencil shown in the illustration. This can be done in 
an instant and with the utmost precision. The ground glass behind h 
serves to destroy the image of outside objects which are formed when 
the aperture li is reduced 
m size. 
Fig. 35. 
The difficulty of using the camera 
lucida with very high powers is 
well known. With this system 
there is no difficulty ; whatever 
cah be clearly seen can be drawn. 
“ When the left-hand table q 
is arranged on a level with the 
Microscope stage, the moving of 
objects on to and off the stage is 
conveniently accomplished. 
“ The sliding adjustment of 
the drawing-board or table (right- 
hand q) will commend itself at 
once to anyone who has used a 
camera lucida. Already a number 
of patents exist on this head, 
but all that I have seen are lack- 
ing in stability and convenience. 
Here, however, the artist may lie 
stretched at ease, and, having so 
adjusted the drawing-board as to 
secure the desired magnification, can work with comfort and with great 
precision. 
“ The nice working of the fine adjustment is facilitated by the fact 
that the ball of the hand may at the same time rest on the table. 
“ The Microscope can be clamped in position, and is movable within 
limits. 
“ The photographic camera is in readiness for instant use, and is as 
rigid as possible. Being arranged on a vertical system, it is most con- 
venient. Few, I imagine, having once fairly tried a good vertical system, 
will ever revert to any other. Its advantages are obvious. For instance, 
the stage remaining horizontal, the object does not tend to float and get 
out of focus ; liquid backing on the plate does not flow ; the focusing 
can be most easily and accurately done, especially when the ground glass 
is dispensed with, and a lens used instead ; the bellows never bothers by 
sagging when long drawn out ; and so forth, and so forth. My whole 
apparatus is made as low as possible, so that in focusing on the ground 
at Z it is only necessary to stand up. If the camera has to be ex- 
Section of heart of Microscope-camera, one- 
lialf size — a, vulcanite shutter; 6, arm 
or lever for opening aud shutting the 
shutter a (this arm is outside the head) ; 
c, slot into which a is set ; d, rabbited 
opening into w r hieh the draw-tube of the 
Microscope fits in a light-tight manner. 
