273 
Art. XI j Cole, Experience with Capillaiy Electrometer, 
To sum up briefly the comparison of leading types of the 
instrument used : For general use in laboratory instruction and 
for projection Ostwald’s second form is to be preferred. This 
can be made sensitive to about .0001 volt and is useful for such 
work as determining resistance by the fall-of-potential method, 
E. M. F. by comparison with a standard cell, current by the 
potentiometer, etc. Ostwald’s first form may be substituted 
where the cost of the reading microscope used with the second 
type is an item of importance, but the superior sensitiveness of 
the second form recommends it. 
For higher sensitiveness, in research work or very exact 
laboratory measurements, the modified Paschen electrometer 
with capillary about .2 mm. in diameter is highly satisfactory 
and better than Ostwald’s third form. 
The experimental work described in this paper was done 
at the University of Chicago and at Denison University. 
Ohio State University. 
