THE SPECIFIC INDUCTIVE CAPACITY OF A DIELECTRIC. 
7 
The fact that both periods give the same value shows that, as was to be expected 
from its crystalline structure, there is no absorption in mica for those short times of 
charging. 
Fig. 3. 
Ehonite. 
The ebonite condenser was made of twenty discs of ebonite, about a third of a 
millimetre thick, and three and a quarter inches in diameter. The ebonite sheets were 
carefully cleaned with paraffin dissolved in benzol, and this gave perfect insulation 
without, any shellac border. At temperatures above 70° C. the capacity began to 
increase rapidly owing to softening. The highest temperature reached in the 
preliminary heating was a little under 80° C. 
The insulation was constantly tested as in the case of mica, and was found perfect 
up to about 70° C. 
The results are given in the following table and diagram (hg. 4). 
As the insulation was perfect, the greater capacity shown by the longer time of 
charging must be due to absorption—an effect which the structure of ebonite would 
lead us to expect. The column of values for instantaneous charge have been calcu¬ 
lated on the assumption that the absorption goes on at the same rate from the 
beginning of the charge, as duriug the interval observed. 
Temperature. 
Variable resist¬ 
ance. 
Change of 
capacity. 
Rate of increase 
per degree. 
1 
Fork making 99 comp 
lete vibrations 
■)er second. 
13“ C. 
3520 
44 
3460 
•017 
•00055 
57 
3415 
•030 
•00068 
63 
3355 
•044 
•00088 
Fork making 64 complete vibrations per second. 
13 
5250 
44 
5143 
•020 
•00065 
57 
5060 
•036 
•00081 
63 
4960 
•055 
•00110 
75 
4800 
•085 
•00170 
