72 Professor CumMinG on the Developement 
TABLE X. 
Conducting powers of Copper Wires of different diameters. Double bar 
of Antimony and Bismuth with the large Compass ; the colder ex- 
tremity in Water at 65°. 
Diameters. 
Length of wires 16 4 inches. 
seo iy Seti coe) 
8 15.6 | 15.3 8.7 Length of wires 1+ inches. 
Deviations. 
When 33 inches of the wires of 4; and -5 were used, the observed deviations 
were 6°.4 and 3°; with 16+ inches of the same wires, they were 6.4, and 4.27; and 
with 14 inches were 6.4, and 5.98; therefore, the difference of their conducting powers, 
which is inconsiderable with short wires, increases very rapidly with their length. 
Hence it is obvious that wires which do not exceed =!,inch in diameter, are 
improper in the construction of instruments for detecting minute Galvanic action ; 
since their loss of conducting power may be such, as to counterbalance any advantage 
arising from the multiplying action of the spiral. 
Six wires of +1; 5 each 164 inches lon 
Four of ..++s> gave the same deviations as one of 4 >'5 ‘ = 
Three of .. + a> =ty each 1 + inches long. 
