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1280.  I endeavoured to find some liquids which would insulate well, and could be obtained in sufficient quantity for these experiments.  Oil of turpentine, native naphtha rectified, and the condensed oil gas fluid, appeared by common experiments to promise best as to insulation.  Being left in contact with fused carbonate of potassa, chloride of lime, and quick lime for some days and then filtered, they were found much injured in insulating power; but after distillation acquired their best state, though even then they proved to be conductors when extensive metallic contact was made with them.

1281. Oil of turpentine rectified.—­I filled the lower half of app. i. with the fluid:  and as it would not hold a charge sufficiently to enable me first to measure and then divide it, I charged app. ii. containing air, and dividing its charge with app. i. by a quick contact, measured that remaining in app. ii.:  for, theoretically, if a quick contact would divide up to equal tension between the two apparatus, yet without sensible loss from the conducting power of app. i.; and app. ii. were left charged to a degree of tension above half the original charge, it would indicate that oil of turpentine had less specific inductive capacity than air; or, if left charged below that mean state of tension, it would imply that the fluid had the greater inductive capacity.  In an experiment of this kind, app. ii. gave as its charge 390 deg. before division with app. i., and 175 deg. afterwards, which is less than the half of 390 deg..  Again, being at 176 deg. before division, it was 79 deg. after, which is also less than half the divided charge.  Being at 79 deg., it was a third time divided, and then fell to 36 deg., less than the half of 79 deg..  Such are the best results I could obtain; they are not inconsistent with the belief that oil of turpentine has a greater specific capacity than air, but they do not prove the fact, since the disappearance of more than half the charge may be due to the conducting power merely of the fluid.

1282. Naphtha.—­This liquid gave results similar in their nature and direction to those with oil of turpentine.

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1283.  A most interesting class of substances, in relation to specific inductive capacity, now came under review, namely, the gases or aeriform bodies.  These are so peculiarly constituted, and are bound together by so many striking physical and chemical relations, that I expected some remarkable results from them:  air in various states was selected for the first experiments.