HIGH ELECTROMOTIVE FORCE 
DESCRIPTION OF THE BATTER \' 
T 
The appliances for research have greatly increased since the time of Faraday; but 
It Is significant that the wealth of means has not contributed much to our knowledge 
of the science of electricity. The advances have come from workers who have not had 
at their command very powerful electrical currents, such as are used in commercial 
applications ; and I am led to conclude that the best equipment of a physical labora- 
tory resides in good minds and not in elaborate installations and large collections of 
physical apparatus. 
Nevertheless a step is made when the limits of application of the present power- 
ful sources of electricity can be shown in such a subject, for instance, as Spectrum 
Analysis. 
Thirty years ago investigators depended upon voltaic batteries for their source of 
electric currents. The limits of electromotive force were necessarily low, on account 
of the expense involved in a plant of a large number of cells, and the labor of setting 
up the cells was very great. In the literature of electricity and magnetism one finds 
a full account of the large experimental battery of de la Rue and Miiller. This con- 
sisted of 8040 elements of amalgamated zinc and chloride of silver in a salt or sal 
ammoniac solution. Each cell consisted of a glass tube 15.23 cm. long and 1.9 cm. in 
diameter. The tube was closed by a rubber stopper to avoid evaporation : the chlo- 
ride of silver paste and a strip of silver constituted the positive pole of the cell. This 
silver strip was carefully protected from the sulphur of the rubber stopper by suitable 
insulation. The electromotive force of each element was 1.03 volts and the internal 
resistance of each cell 38.5 ohms. The total electromotive force of the battery was 
approximately 8281.2 volts. De la Rue and Miiller recommend such an installation 
for use in spectrum analysis. 
Before entering upon a more detailed account of a much larger installation I will 
give here, for comparison, similar data in regard to this installation. 
The cells of the battery in the Jefferson Physical Laboratory number 20,000 ; the 
glass tubes of each cell are 14 cm. long, 1.9 cm. in diameter, -not differing therefore 
much in size from the de la Rue and Miiller battery. The electromotive force of 
