266 Bulletin of Laboratories of Denison University [Voi. xi. 
the volume of Ostwald. It struck me that it ought to be a 
first rate instrument for use in the physical laboratory for a 
great variety of purposes. An experience of several years, 
which includes a study of its practical fitness for use in meas- 
urements usually made with costly electrometers and galva- 
nometers, has strengthened that first impression. Among the 
advantages which may be fairly claimed for the capillary elec- 
trometer are 'the following : 
1. It is wholly unaffected by any magnetic disturbances 
in its neighborhood and far less sensitive to mechanical vibra- 
tions than any galvanometer or electrometer of equal sensitive- 
ness. So it is possible to use it in the immediate vicinity of 
powerful dynamos or electromagnets. 
2. It far excels any other forms of electrometer, whether 
of attracted-disc or quadrant type, in sensitiveness. It can 
be made to show .00001 volt and easily measures .0001 volt. 
It is also much more free from disturbance by accidental electro- 
static changes in the neighborhood than is a quadrant elec- 
trometer. 
’ 3. It is extremely dead beat, the setting of the instrument 
requiring only a very small fraction of a second. 
4. It is so sensitive that it may replace a high-resistance 
reflecting galvanometer for many purposes, and with the great 
advantage, that it takes no current at all from the circuit being 
measured. 
5. It is much smaller, lighter, more portable, more easily 
and quickly set up — in general more convenient — than any 
other' form of electrometer. 
6. It is cheap and readily constructed by the experi- 
menter for himself. It is indeed almost ridiculously cheap in 
the simplest form. A capillary electrometer costing a dime for 
materials and a half hour’s labor will excel a $2^0 quadrant 
electrometer in sensitiveness. Enough of them can be quickly 
prepared for the use of a large class of students at a nominal 
cost. 
7. The extreme quickness with which it follows fluctua- 
tions in potential difference enables it to do some things that 
