152 Proceedings of Indiana Academy of Science. 



Fig. 1. 



M. 



Fig. 2. Median longitudinal sectional view of tli( 



4-- 



dor-k. Natural 



Fig. 3. Top view of nrass block, natural size. 



caused inaccuracies in tlie ttiickness 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 cut 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 contriv- 

 ance which at the same time insured accuracy and uniformity. The micro- 

 tome I used is provided with a brass cogwheel 7.5 cm. in diameter, a cir- 

 cumference of 235.6200 mm. and having on its periphery 100 cogs (A Fig. 1). 

 This cogwheel is attached to a threaded shaft which moves the paraflBn 



