H, A, Rowland—Absolute Unit of Electrical Resistance. 288 
the damping of a swinging needle. Three experiments gave 
for the resistance of the circuit 1903-108, 1898-108, and 1900-108 
mine ; ° . 
—, but it is to be noted that a correction of five eighths per 
cent was niade on account of the time, two seconds, which it. 
took to turn the earth-inductor, and that no account was taken 
of the temperature, although the material was copper. He finds 
for the value of the Jacobi unit, 598-107 a Three years after 
that, in 1853, Weber made another determination of the spe- 
cific resistance of copper.* But these determinations were 
more to develop the method than for exact measurement, and 
it was not until 1862+ that Weber made an exact determina- 
tion which he expected to be standard. In this last determin- 
ation he used a method compounded of his first twoemethods 
by which the constant of the galvanometer was eliminated, and 
the same method has since been used by Kohlrausch in his 
experiments of 1870. The results of these experiments were 
embodied in a determination of the value of the Siemens unit 
and of a standard which was sent by Sir Wm. Thomson. As 
The matter was in this state when a committee was appointed 
by the British Association in 1861, who, by their so pevenen 4 
which have extended through eight years, have done so mac 
in the magnetic meridian also causes re 
volving coil which deflects the needle from that — 
Whenever a conducting body moves in a magnetic le is 
rents are generated in it in such direction that the total re- 
* Abb. d. Kon. Ges. d. Wissenschaften zu Gottingen, Bd. 5. : : 
+ Zar Creivimcstattie; Gattingen, 1862. Also Abh. d. K. Ges. d. Wis. zu Got- 
tingen, Bd. 10. 
