378 



THE AMERICAN MONTHLY 



[D. 



ajierture in the table is also provided witli the iiKMallic 

 grating, and the fluororneter is provided with an attacli- 



ment which closes tlie side of the instrument wliich was 

 oi)en dnring the first observation. Now, when the snr- 

 geon takes a position below the table, he obtains a view 



