ON STANDARDS FOR USE IN ELECTRICAL MEASUREMENTS. 111 
The values of ¢ are given in terms of the coils of the legal ohm box 
at 17°. Hence the capacity found needs to be divided by 1:0014 to reduce 
it to legal microfarads, and it then becomes ‘020995. 
Moreover, since 1 legal ohm=1:01124 B.A.U., and 1 B.A.U.=:9866 
x 10° cm. per sec., we have 
1 legal ohm = ‘9977 x 10° cm. per 1 sec. 
And the absolute electro-magnetic measure of the capacity of the con- 
denser I. is 
021043 x 10-"* sec.? cm.!. 
: The effect of the leak in condenser II. was still further investigated 
on August 28. The plates of IJ. were connected by a resistance of 30 
megohms. Hence the correction to c, which is 
— becomes —-000520 x 10-5, when n=64. 
nN 
The value of c found with the leak in was :023813 x 10-". 
Hence making the correction c=:02249 microfarad, which is suffi- 
ciently close to the value found without the artificial leak. 
Table III. shows that with mica condensers not very much greater in 
separate capacity than the air condensers a change in the frequency of 
the charge from 21 to 80 produces an appreciable change in the capacity. 
This, of course, is in consequence of the absorption. With large con- 
densers, as we have already seen, the effect is more marked. 
It remains, then, to give an account of the experiments undertaken 
for the purpose of comparing mica or paraffin condensers as ordinarily 
used with the air condensers, and of investigating some of the effects of 
absorption. 
The two well-known methods of De Sauty and Sir William Thomson 
have both been employed. 
The arrangements are shown in Figs. 6 and 7. 
FIia. 6. 
Cr 
Ai 
Ao 
Ke Bs 
_ The first of these is not really suitable for use in cases in which there 
is absorption, though, with care, a fairly accurate measure of the instau 
