626 



Transactions of the Society. 



into contact, an electric circuit is completed through a battery 5, 

 a resistance r, a telephone receiver te, a nut n, and thence through 

 the screw sc and the stage s to the battery. At each make or 

 break of circuit at the point t the telephone "speaks." 



In order to measure any object seen in the Microscope slide, 

 move the stage by the rack-and-pinion or other adjustment, till 

 the cross-wire is on one side of the object. Bring the screw sc into 

 contact with stage s, and when the telephone speaks observe the 



Fig. 12G. 



reading E x of the disc d. Now move the stage till the other side 

 of the object coincides with the cross-wire. Bring the screw into 

 contact again, and obtain a new reading B 2 of the disc d. Then 

 the diameter of the object is (B 2 — B x ). $*m£ 



As an example, three sets of readings were taken for Bacillus 

 tuberculosis, and were as follows : — 



