506 Mr. J. Swinburne on the Electrometer as a Wattmeter. 



makes the correction for which the second reading was neces- 

 sary in fig. 1, so the instrument can be graduated in watts. 



Fig. 2. 



fWW 



y o^-t-y 



WAAi 



There may be some slight error due to the whole needle 

 being drawn into the quadrants a and b, and out of c and d. 

 This is obviated by making the needle of such a shape that 

 there is no appreciable end pull, as shown in fig. 2. 



Fig. 3 shows a form for a direct-reading instrument with 

 Fig. 3. 



a pointer or index. Instead of quadrants it has half-disks, 

 like the Blondlot and Curie electrometer, but, unlike it, this 



