10 
MR. W. CASSIE ON THE EFFECT OE TEMPERATURE ON 
Rate of chano'e corrected for mstaiitaiieoiis charo^e. 
O O 
17° to 38° 
•0013 
49 
•0010 
57 
•0010 
62 
•0015 
Fig. 5. 
The next three tables and diagram give the results of experiments upon another 
condenser of microscope-slide cover-glass. This specimen of the glass had less con¬ 
ductivity than the previous, but the precautions for general insulation were not equal 
to those in the other experiments described. The condenser rested on a glass tripod 
inside the air bath, and the leading wires passed into the bath through glass tubes. 
The condenser consisted of twenty-two discs of glass cleaned and bordered with 
shellac in the usual way, with discs of lead foil between them. 
The curves are almost exactly parallel up to between 40° and 50°, and diverge at 
higher temperatures in consequence of conduction ; so that we may take the tempera¬ 
ture change of specific inductive capacity for this specimen of glass to be about '2 per 
cent, up to 50°, 
An attempt was made to observe this temperature efiect for shellac. The condenser 
was made by dipping the lead discs in shellac varnish, and carefully and thoroughly 
evaporating the alcohol. But after the condenser was made it was found that at a 
temperature below 50° the shellac softened, so that the plates were pressed together 
by the weights on the top of the condenser. To diminish the weight would have been 
useless ; because, in any case, it would have been impossible to say how far a change 
of capacity was due to softening, and without a weight at all tlie results are quite 
unrelialfie. 
