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 ries, relative to the altitude, motion, velocity, &c. and even the very nature itself, of that I had so transient a view of, might perhaps be deducible from it.

Instances of Auroræ Australes, at least in our part of the world, are immensely rare. At present that observed by John Martyn, M. D. F. R. S. and Professor of Botany in the University of Cambridge, only occurs. The account of this very uncommon appearance, transmitted by that ingenious gentleman to the Royal Society, and published by them in the Philosophical Transactions, highly merits the attention of the curious meteorologist. This phænomenon, seen by him, January 23, 1749-50, and that of which I now send you so imperfect a description in several respects pretty well agreed; but in others, which it would be superfluous even to touch upon here, almost totally differed. Some of the public papers informed us, that an extraordinary phænomenon was observed in the air at London, the preceding night, viz. March 4, 1764; which in a few particulars resembled that of which I have taken the liberty to communicate to you a short account in this letter, but in the rest those two meteors were dissimilar enough. Perhaps these Auroræ Australes may some time or other hereafter be more frequent than hitherto they have been, and by certain new circumstances attending them farther elucidate the theory of this species of meteors; the true cause of which, notwithstanding the labours and researches of several learned