152 Proceedings of Indiana Academy of Science. 
Wig. 1. 
Fig. 2. Median longitudinal sectional view of the brass block. Natural size. 
3 
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Fig. 3. Top view of brass block, natural size. 
caused inaccuracies in the thickness of the sections that were cut. This 
latter was caused by weakness in the springs, one of which controlled the 
ratchet of the cogwheel, and frequently on account of this the cogwheel 
was not turned the specified distance. Sometimes the sections were cut too 
thin or the block was not set out for cutting at all. At other times a notch 
in the cogwheel was skipped causing the section to be ent too thick. 
The above mentioned imperfections of the system of springs for adjusting 
the thickness of the sections was overcome by the use of a simple contriy- 
ance which at the same time insured accuracy and uniformity. The micro- 
tome I used is provided with a brass cogwheel 7.5 em. in diameter, a cir- 
cumference of 235.6200 mm. and haying on its periphery 100 cogs (A Fig. 1). 
This cogwheel is attached to a threaded shaft which moves the paraffin 
