Light and Heat

Sir John Leslie · Confusing Words Series · 4 pages

The shortest file in the series: a single quotation and its source. It is taken from a footnote in The Secret Doctrine I, where Blavatsky quotes Sir John Leslie's An Experimental Inquiry into the Nature and Properties of Heat of 1804, and the claim is that there is no fundamental difference between light and heat at all — each is merely a metamorphosis of the other.

The formulation Leslie gives is the reason the passage was picked out for a series on words people confuse: heat is light in complete repose, and light is heat in rapid motion. What follows explains the mechanism as he saw it — that when light is directly combined with a body it becomes heat, and when it is thrown off from that body it becomes light again. The remaining pages are the standing apparatus of this series, the suggested reading and the list of the other commonly confusing words.

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