PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 925 



and my true tangent galvanometer, I have obtained the following 

 results: The galvanometer coil for intensity is of fine wire, and 

 gives 3.4 miles resistance; that for quantity is a simple plate of 

 sheet copper whose resistance is so small that it need not be taken 

 into account. The interior resistance of the cups is about 0.2 

 miles each. 



First case : 



Compound or intensity battery., with intensity galvanometer, and 

 a rheostat resistance of 20 miles. (My unit of resistance is that 

 of one mile No. 8 galvanized iron wire.) The deflection given 



By one cup was 16*^ 



By two cups 29° 15' 



Bythreecups .,. 38° 05' 



Byfourcups _ 46° 45' 



The increasing interior resistance prevents the forces from being 

 quite proportional to the number of cups ; for the tangents of 

 these deflections show that the mtensity of four cups, compared 

 with that of one, is as 3.7 to J. 



Second case : 



Compound battery, with quantity galvanometer and short, thich 

 connecting wires. The deflection given 



By one cup was 10° 30' 



By two cups 10° 10' 



Bythreecups 9° 40' 



By four cups 9° 



In this case we see that the quantity diminishes as we increase 

 the number of cups, which is due to the increasing interior resist- 

 ance; that for one cup being two-tenths mile, and that for four 

 eight-tenths — showing how little capable, as stated above, a quan- 

 tity current is of overcoming resistance. One hundred and 

 twenty cups at the Western Union office gave deflection of only 

 5° 20'. 

 Third case: 



Sinij)h {or quantity) battery, with intensity galvanometer. — The 

 deflections were as follows : 



One cup 61° 



Two cups 61° 40' 



Three cups 62° 20' 



Fourcups : 62° 50' 



