336 H. A. Rowland—Absolute Unit of Electrical Resistance. 
the consequent difficulty of their accurate measurement. A 
comparison with the electro-dynamometer has such a small 
probable error, and as it is a much larger coil, it seems best to 
give this number twice the weight of that found by calcula- 
tion: we thus obtain 
G = 1833-19 
as the final result. 
It does not seem probable that this can be in error more than 
one part in two or three thousand. 
lescope, scale, &c.—The telescope, mirrors and plane-par- 
nations was the mean distance. In using the coils they were 
always used in all four positions. The probable error of each 
set of twelve readings was +001 mm. The data are as fol- 
lows, naming the coils A, B and C: 
Mean radius of A=13°710, of B=13°690, of C=13°720. 
Mean distance apart of A and B=6°534, of A and C=9°574, of 
B and C=11°471. 
N=154 for each coil, E=-90, n=-84. 
For A and B we have 
M=3774860°+ 3, (74250°—665 10°)=3775500° 
The remaining terms of the series are practically zero, as was 
found by dividing one of the coils into parts and calculating 
the parts separately and adding them. 
or A and C 
M=25614 10°-+-1,(34000- —27230°)=2561974° 
For B and C 
M=2050600-+-1,(27500°— 19800°)—=2051320° 
The calculation of the elliptic integrals was made by aid of the 
tables of the Jacobi function, g, given in Bertrand’s “Traité de 
Calcul Integrale” as well as by the expansions in terms of the 
modulus after transforming them by the Landen substitution. 
[To be continued.] 
