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SCIENCE—ADVERTISEMENTS 
SPENCER 
ABBE Camera Lucida No. 500 
It shows the WHOLE of the Field. The 
Object and the Pencil Point CLEARLY. 
Advantageous Features 
Unique compact mounting makes it possible to place the eye sufficiently close 
to the prism so that the pupil takes in all of the divergent rays coming 
from the whole of the field of the ocular, making the field appear as large 
and the object very nearly as distinct as when viewed without the camera. 
The prism can be so centered by two concentric screws that the field is free 
The smoked glasses are so mounted around and below the prism that the 
light from the pencil and the object can be easily modified to make them 
The prism is so mounted that the opening in the silvering can be lowered in 
the case of the higher power oculars or raised with the lower powers until 
I, 
II. 
from color to the extreme edge. 
III. 
equally distinct. 
IV. 
it comes to the exact focus of the ocular. 
Vv. 
I¢ has a very large mirror (70 mm.x105 mm.) supported on an adjustable 
graduated mirror bar. 
IT SATISFACTORILY SOLVES AN HERETOFORE UN- 
SATISFACTORY METHOD OF MICROSCOPIC WORK 
Samples gladly submitted for examination 
SPENCER LENS COMPANY 
BUFFALO, N. Y. 
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