434 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
??, wooden front or head of camera, into which the barrel of the Micro- 
scope fits. This head is hollowed out, and carries a light ebonite 
shutter, actuated from the outside, by means of which the exposures 
are made. The wire lever actuating this shutter is shown as a dotted 
white line near n (see also fig. 35). 
o, mirror of the Abbe camera lucida. 
2 >, barrel of the Microscope. 
q q, vertically sliding tables, the right-hand one being used as a drawing- 
board when the camera lucida is in use. Being adjustable, various 
magnifications can be secured. The higher q is placed the less 
magnification the drawing will show. A scale drawn on the archi- 
traves enables any position of q to be registered. The left-hand table 
is similarly adjustable, and is usually kept on a level with the 
Microscope stage. Both these sliding tables are cut away to suit the 
observer’s body resting on the stool v. Both are braced so as to be 
quite rigid under the weight of the arms in drawing, &c. 
r, head into which the foot of the Microscope is firmly clamped by means of 
easily removable wooden wedges. 
s , pillar bearing the Microscope, preferably of iron and planted in cement 
beneath the building, and coming through the floor without contact 
with the building. If this is not feasible, r may be fixed to the 
window-sill. In three of my laboratories the ways c c are fixed to iron 
or wooden beams, also planted in the earth and coming through the 
floor without contact, thus making a very perfect arrangement for long 
photographic exposures with high powers where all tremor must be 
avoided. 
t f, halves of wooden hand-clamps of large size (15 in. long and 2£ in. square), 
grooved to slide in the ways u u, and carrying the well-braced 
tables q q. 
u u, two wooden table-ways, firmly fastened to the side of the building. 
v , stool. 
ic, set-screw, to clamp the camera in position. 
x x , four set-screws, to clamp the tables q q in position. 
y, opaque cloth, sewed on to a rectangular opening cut in the board / to 
admit the light to the mirror of the Microscope. Slots to hold coloured 
glasses are arranged on the back side of this opening, to furnish mono- 
chromatic light for photography, &c. The various substage adjust- 
ments can be worked through the cloth, which, however, can be lifted 
in a second when necessary. 
“ After having made the different features of the drawing (fig. 34) 
clear, it will only remain to explain some of the advantages of this 
system of utilising the Microscope. Having used the Microscope for 
purposes of investigation almost daily for nearly twenty-five years, I 
feel justified in calling particular attention to opinions based on such 
extensive experience. 
“ The apparatus is adapted to the best of all lights — daylight. The 
perfection of the image as formed on the retina of the eye is very great ; 
for if the room be darkened, and the blind d be closed, no light but that 
from the Microscope enters the eye. Few, even among experts, according 
to my observations, realise the evil effects of extraneous light when 
observing with the Microscope. Those who do realise this evil are 
usually found advocating the use of artificial light by night so as to 
avoid the evil. Here is a way to avoid it and still keep to the use of 
daylight. It need scarcely be pointed out that the cloth y is for the 
purpose of excluding extraneous light. 
“ The window faces the sun, so that, whenever it is desired, by simply 
raising the blind d , sunlight can he obtained on the top of the stage as 
well as under it. 
