2B4 Mr. Nicholson’s 'Experiments and 
as meafured by the explofive fpark, is as the thicknefs, when 
the charges are equal, as Mr. Cavendish has determined, and 
I find like wife by experiments with thin fubftances ; but when 
the thicknefles are greater, it increafes in a higher proportion, 
as is found by the explofion which takes place between the 
eleCtrophore and its plate, as well as by other experiments. 
35. This uncompenfated part of the charge (which is com- 
monly in proportion to the quantity of latent or compenfated 
eieCtricity, or to the diftance at which it exerts its aCtion) was 
found to be greatly increafed when a feries of jars were made to 
charge each other. If a jar be infulated and made to explode by 
Lane’s eie&rometer at a determinate number of turns ; and 
another jar be then connected with its external coating fo as to 
become charged by that means, the explofion, from the outfide 
of the laft to the in fide of the firft, will take place at the 
electrometer (unaltered) with much fewer turns. Or if the 
electrometer be altered till the explofion takes place at the ori- 
ginal number, the diftance will be much greater than before. 
Hence we fee, that the intenfity of the uncompenfated part 
muff be greater when there is a greater charge to be main- 
tained, whether it be on one furface only, or on two furfaces 
fucceffively connected. I have not yet made the experiments 
neceffary to afcertain the lav/ of this laft aCtion. 
36. It is evident, that the breaking of jars is not effeCted by 
any attraction between the electricities which form the charge, 
but by this neceffary furp'lus : for thicker glaffes require much 
iefs eieCtricity to produce an intenfity which breaks them than 
thinner do ; and I found a piece of Mufcovy talc, one hun- 
dredth of an inch thick, to bear a charge confifting of ten 
times the quantity of eieCtricity which was fufficient to have 
charged an equal furface of common glafs fo as to break it, 
^ ... But 
