10G NATURALISTS’ ASSISTANT. 
from the paper beneath passes through the prism and enters 
the eye in the same direction as the first. ‘These lines of 
light are represented by dotted lines in the figures. It will 
thus be seen that the eye perceives the object under the 
microscope and a paper placed beneath, superimposed upon 
one another. Its method of use is as follows: the micro- 
scope is first focussed upon an object and then the tube is 
brought to a horizontal position, the camera attached to the 
eye-piece and a paper placed on the table beneath the camera. 
Then looking down through the camera, one perceives at the 
same time the paper and the object. A pencil may now be 
made to trace on the paper the outlines of the object, and 
the details afterward filled in free hand. 
In the first figured camera the image by the two reflections 
is first reversed and then reversed again, bringing’ it the same 
as that seen by direct observation through the tube, giving 
an outline, the details of which are easily filled in. 
The second form having but a single reflection produces a 
reversed image, and hence it is difficult to complete free 
hand. Instead of a prism, the student may easily make his 
own camera of this second form by mounting a piece of thin 
glass in a bit of cork which can be affixed to the tube of the 
microscope. 
A third form, which is rarely seen in America, but which is 
in the opinion of the writer the best, is the “vertical”’ camera, 
manufactured by Carl Zeiss. ‘This form may be applied to 
the microscope when in a vertical position, throwing the im- 
age to one side of the stand, and giving the clearest image 
of any, of both object and pencil. It is also remarkably cheap 
