Page:Proceedings of the Royal Society of London Vol 4.djvu/63

Rh suming the capacity of the air apparatus as unity, that of the shell

lac apparatus would be 176/113 or l 55

When the shell-lac apparatus was first charged, and then the charge divided with the air apparatus, it appeared that the lac appa- ratus, in communicating a charge of 1180, only lost a charge of 86 This result gives 1 37 as the capacity of the lac apparatus.

Both these results, the author considers, require a correction; the former being in excess, the latter in defect. Applying this cor- rection, they become 1.50 and 1 47. From a mean of these and se- veral similar experiments, it is inferred that the inductive capacity of the apparatus having the hemisphere of lac is to that with air as 1.50 to 1

As the lac only occupied one half of the apparatus containing it, the other half being filled with air, it would follow from the foregoing result, that the inductive capacity of shell-lac is to that of air as 2 to 1

From all these experiments and from the constancy of their results the author deems the conclusion irresistible, that shell-lac does ex hibit a case of specific inductive capacity.

Similar experiments with flint-glass gaveits capacity l-76 timesthat of air. Using in like manner a hemisphere of sulphur, it appeared that the inductive capacity of that substance was rather above 2-24 times that of air, and the author considers this result with sulphur as one of the most unexceptionable.

With liquids, as oil of turpentine and naphtha, although the re- sults are not inconsistent with the belief, that these liquids have a greater specific inductive capacity than air, yet the author does not consider the proofs as perfectly conclusive.

A most interesting class of substances, in relation to specific in- ductive capacity, the gases or aeriform bodies, next came under the author's review.

With atmospheric air, and likewise with pure oxygen, change of density was found to occasion no change in the inductive capacity Nor was any change produced, either by an increase of temperature or by a variation in the hygrometric state.

The details are then given of a very elaborate series of experiments with atmospheric air, oxygen, hydrogen, nitrogen, muriatic acid carbonic acid, sulphurous acid, sulphuretted hydrogen, and other gases, undertake with the view of comparing them one with an- other under a great variety of modifications. Notwithstanding the striking contrasts of all kinds which these gases present, of property, of density, whether simple or compound, anious or catious, of high or low pressure, hot or cold, not the least difference in their cupacity to favour or admit electrical induction through them could be per- ceived. Considering the point established, that in all these gases induction takes place by an action of contiguous particles, this is the more important, and adds one to the many striking relations which hold among bodies having the gaseous form.