1878.] 
The British Association. 
527 
terval elapsing since charging increases, therefore the rate 
of conversion of electric energy into heat, that is, conduction, 
also grows less and less, and therefore it is correct to say 
that the resistance of a dielectric does really increase by 
electrification. Besides this there is, of course, some of the 
absorbed energy which is recoverable, and which, therefore, 
must not be confounded with conduction ; just as the energy 
recoverable from a deflected beam must be distinguished from 
that lost through conversion into heat, on account of internal 
friction. From the curves we have obtained of the charging 
of condensers, and assuming that there is no discontinuity, 
we must assume that even the first charging is itself a very 
rapid absorption, and since there is viscosity, even the very 
first charging must be accompanied with a generation of 
heat— that is, true conduction. Also, since it is known that 
gases, like all other substances, are to a certain extent 
viscous, we cannot believe that air and other gaseous con- 
densers show absolutely no absorptive phenomena; in faCt, 
sufficiently accurate experiments have not yet been made on 
the subject. We conclude, therefore, that the less the spe- 
cific resistance the greater is its molecular plasticity, and 
the more plastic the substance is the greater will be the first 
charge ; therefore from the stress and strain analogy it fol- 
lows that the less the specific resistance of a substance the 
greater will generally be the specific induCtive capacity. In- 
fluenced by these ideas we examined experimentally the 
specific resistance ofseveral dielectrics, and were eventually 
able to compare the specific induCtive capacities and specific 
resistances of dilute sulphuric acid, mica, gutta-percha, 
shellac, Hooper’s material, ebonite, paraffin-wax, glass, air, 
and we found that if the above substances were arranged in 
descending order of specific induCtive capacity they were 
found arranged in ascending order of specific resistance. 
Again, since the resistance of air to eleCtric discharge is less 
than that of a Sprengel vacuum, we were theoretically led 
to expert (in contradiction to the results of Faraday, who 
concluded that the specific induCtive capacities of all gases 
at all temperatures and pressures were identical) that very 
accurate experiments would show that different gases had 
different specific induCtive capacities. This result we were 
experimentally able to verify after months of investigation, 
and we found that the denser the gas the higher the specific 
inductive capacity, a vacuum having the least capacity of 
the substances we experimented on. It was our intention 
at that time to determine accurately the eleCtric capacity of 
a Crookes’s vacuum, an investigation I hope to complete 
