Thoreau writes in his journal:
Some geniuses seem to hover in the horizon, like heat lightning, which is not accompanied with fertilizing rain to us, but we are obliged to rest contented with the belief that it is purifying the air somewhere. Others make known their presence by their effects, like that vivid lightning which is accompanied by copious rain and thunder and, though it clears our atmosphere, sometimes destroys our lives. Others still impart a steady and harmless light at once to large tracts, as the aurora borealis; and this phenomenon is hardest to be accounted for some thinking it to be a reflection of the polar splendor, others a subtle fluid which pervades all things and tends always to the zenith. All are agreed that these are equally electrical phenomena, as some clever persons have shown by drawing a spark with their knuckles. Modern philosophy thinks it has drawn down lightning from the clouds.
