Dangerous Moonlight, Black Air and Marginalia

At Day's Close: A History of Nighttime by A. Roger Ekirch had been languishing on my bookshelves for some while, largely because it's such a damn'd thick, square book. But then, the other day, it occurred to me that if ever there was a book for bedside reading, this was it.
  I haven't got far into it yet, but am enjoying its wide-ranging and, er, illuminating treatment of its subject – the nighttime world of our pre-industrial ancestors. I was reading the other night about the fearful power attributed to the moon, which could so disorder the 'moistures' in a person's body as to turn them into 'moonstruck' lunatics, or even strike them dead. 'The moon,' writes Ekrich, 'also impregnated the night air with pestilential damps, widely deemed an even graver menace to human health. Darkness signified more than the temporary absence of light. According to popular cosmology, night actually fell each evening with the descent of noxious vapours from the sky.... Some individuals described themselves 'within night', as if enveloped my a mammoth black cloud.'
  This sounded familiar... Of course – the philosopher de Selby (known only from commentaries on his works) in Flann O'Brien's The Third Policeman had rather similar ideas about the nature of nighttime. Darkness, he declared, was 'simply an accretion of "black air", i.e. a staining of the atmosphere due to volcanic eruptions too fine to be seen with the naked eye, and also to certain "regrettable" industrial activities'. As for sleep, that was 'simply a succession of fainting fits brought about by semi-asphyxiation' caused by the 'black air' of nighttime. As various of de Selby's commentators point out, there are one or two problems with this theory – not least that darkness can be instantly dispelled by striking a match or turning on a light. De Selby's answer to this was that 'black air' was 'highly combustible, enormous masses of it being instantly consumed by the smallest flame, even an electrical luminance isolated in a vacuum'. However, his strenuous efforts to bottle 'black air' in containers of black glass or opaque porcelain seem to have come to nothing. The commentator Bassett took de Selby's 'black air' theory as 'final proof that the great brain was out of gear'. A few centuries earlier, he might have been taken more seriously.

As for my daytime reading, this has been devoted largely to a novel of which I'll be writing later. My copy is amusingly embellished with pencil-written annotations by a tireless Welsh pedant whose self-appointed mission is, it seems, to correct all Anglicised Welsh names back into their unsullied original forms. He also finds time to correct any perceived errors of fact. How very thoughtful of him.