An Account of a Pyramidal Appearance in the Heavens, Observed Near Upminster in Essex, by the Reverend Mr. William Derham, F. R. S.

III. An Account of a Pyramidal Appearance in the Heavens, observed near Upminster in Essex, by the Reverend Mr. William Derham, F. R. S. Upminster, April 7, 1707. The Afternoon of Thursday April 3 last, I devoted in some measure to the Service of the Royal Society, to take Angles, in order to finish my Observations about Sounds. And as I was returning home, I perceived in the Western part of the Heavens, about a quarter of an Hour after Sun-set, a long slender Pyramidal Appearance, perpendicular to the Horizon. The Base of this Pyramid I judged to be doubtless the Sun (then below the Horizon.) Its Apex reacht 15 or 20 Degrees above the Horizon. It was throughout of a rusty red Colour; and when I first saw it, pretty vivid and strong; but the top-part fainter much than the bottom, nearer the Horizon. At what time this Appearance began, whether at, or how soon after Sun-set, I cannot say, being at that time in a Friend's House. But about a quarter of an Hour after Sun-set, as soon as I was gotten abroad, I perceived it, and had for some time a fair Prospect of it, the Horizon being pretty free and open where I then was. But after a while, it grew by degrees weaker and weaker, so that in about a quarter of an Hour after I first saw it, the top-part (a. b. d. in Fig. 1.) was scarce visible. But the lower part remained vivid much longer, but yet grew by degrees shorter and shorter. I saw the Remains of the lower half (b. d. e. f.) a full Hour after Sun-set; and should perhaps have seen it longer, had the Horizon been open. But it was often in my Walk pent up with Trees, which not only only obstructed my sight of the end of this unusual Appearance, but also hindered me from an exquisite Observation of all the Particulars that might probably occur. The whole Atmosphere seemed hazy, and full of Vapours, especially towards the Sunset. The Moon and Stars were that Evening bearded at that time, and succeeded with an Halo about the Moon afterwards. Which disposition of the Air was probably the cause of the Phænomenon. But the Pyramid was undoubtedly imprinted upon the far distant Vapours of the Atmosphere; it being manifestly farther off, or lying beyond some small thin Clouds (c. l. c. l.) that intercepted it, and in those parts covered and hid it. Altho' I have the greatest part of my Life been ready enough to take notice of such Appearances, yet I do not remember I ever saw any thing like it, except the white Pyramidal Glade, which is now entituled by the Name of the Aurora Borealis. And it being (except in Colour and Length) so like that, I have thought it worth your cognizance, and, if you think fit, of our most illustrious and famous Society also; because it may perchance in some measure conduce to the Solution of that odd Phænomenon, the Aurora Borealis. I was just going to give you some of my Observations about the Migration of Birds this Year, which makes me hope, that that Subject is within the reach of the Royal Society to discover. But being prevented, I have not time just now, but shall reserve it for a more convenient Opportunity, when I have more leisure. I have searched every Night since for this Pyramis Vespertina, but have not seen any such Appearance, although the next Evening was hazy and likely. I also looked out to see whether the Aurora Borealis would succeed in the room thereof, but discovered no such thing. IV. An