H. A. Rowland—Absolute Unit of Electrical Resistance. 485 
respect to each other, followed by another comparison of resist- 
ance with standard. 
5th. Biestrediaub of a and # were again made as before. 
6th. The time of vibration was again determined. 
The observations as here explained furnished data for three 
computations of the resistance of the circuit, one with each of 
the three currents. In each of these three a ete a was 
the mean of 16 readings, 8 of 8 or sometimes 12, @ of 16 and d 
of 16. Ta using the method of recoil nearly the same order 
was observe 
The time of vibration was determined by allowing the needle 
to vibrate for about ten seconds and making ten observations 
of transits before and after that period. During the experiment, 
I usually observed at the telescope and Mr. Jacques at the tan- 
gent galvanometer. 
The methods of obtaining the corrections require no explan- 
ation. 
Results. 
The constant corrections are as follows for the first needle. 
a= —A+1°= —-00711 
b= Meee ~ Sh 
sal Cy oe + °00003 
f= + 00003 
a fy Pes ore e+f= —-00718, 
For method of recoil it becomes — 00016. 
Hence for A and B, log K=11-45360380 
‘ A and C, log K=11-2852033 
“ — * Band C, log K=1171886619 
For method of recoil using A and B, log K=11°4566630. 
For second needle and method of recoil, 
a=—} z)= — 000050 
J= +00 
a+b+ ai ee ye —-00017 
For A and B, log K=11°4566587 
* A and C, log K=11-2882590 
“ B and on log K=11 1917176 
The distance oF the mirror from the scale varied between 
192-3 and 193°5 cm 
