( 221 ) 
the following measurements. As only the differences of capacity are 
required we put the capacity in the position 8.40 as 0, in the 
position 15.05 as 1 ete, i.e. we take that of the calibrating con- 
denser as unity. The corresponding numbers are given in the first 
column of the above table, from which intermediate values can be 
obtained by graphic interpolation. 
As a control of the accuracy of the calibration values given in 
Table I the following work was undertaken. Measurements were 
made with another condenser in the same manner as before 
with the calibration condenser, but the connecting wire was about 
12 em. long and had hence a relatively large capacity. Let ¢ be 
the capacity of this condenser, d that of the wire and y that of the 
electrometer together with its leads, which were unaltered throughout 
the experiment. Further let 29, zj, 7g.... be the capacities of the 
adjustable condenser which correspond to the different positions of 
the glass plate obtained in the calibration. Hence, when the condition 
that the needle is in equilibrium is fulfilled, we have | 
ty Ade U AC 
OER ke Re 
from which we have immediately 
1 an SEEN Ee 
Korne at Hal ee Niel AEG eek vb 
7 ty ae 
ae ables oie, (CNE tO) 
hence the consecutive displacements of the glass plate are proportional 
to one another. The numbers given in Table IL were obtained in 
this manner and each is the mean of three values as satisfactory 
PUB el Wc Died i 
Position Capacity Capacity 
of the Diff, 
glass plate. observed. calculated. 
52 25 7.000 — _— 
1.439 
61.80 8.439 8.440 0.001 
1.475 
71.80 9.914 9.933 0.019 
1.573 
81.77 11.487 11.485 0.002 
1.612 
01.02 13.099 15.099 0.000 
1.684 
99.61 | 14.783 14.775 0,007 
1.743 
107.46 16.526 16.516 0.010 
1.809 | 
1)4.81 | 18,330 | 18,825 0.005 
