E. Cutter—Microphotography with Tolles's Objective. 97 
all ranged in one line. By means of the brass furrow in the 
base board the distances between them were changed without 
getting outof line. The sunlight, the chemicals, and all else had 
previously been found in working order by practical tests. 
Sunlight was thrown by the mirror through the condenser on 
the object which was placed just beyond the heat focus. 
We found that the brightest and clearest days, before 3 P. M., 
were the best. One observer, with his head and the camera 
covered with a black cloth, noted the projection of the image 
on the glass-ground plate. Another fingered the fine adjust- 
ment, or it was done by the focussing rod. When the image 
was satisfactory a card board cut off the light by interposition 
between the condenser and the object. The sensitized plate 
then replaced the glass plate and exposed, the regular exposure 
was made by lifting the card board and letting it fall in the 
course of half a second or more. The time varies and must be 
and instruct the printer how much exposure was need oe 
In photographing yeast with the 7, inch objective the object 
was wet and covered with a film of mica. The following facts 
Requires the aid of a powerful condenser. Usually it works 
best with a B eye-piece as a condenser under the stage, and 
with the thin edge of a common coal-oil flame shining “direct” 
a sort of awe. In our opinion the question is not settled, 
though we think something toward it has been done. As far as 
Am. Jour. Sct.—Tarrp Serres, Vou. XVIII. -No. 104, Aucust, 1879., 
7 
