XVII. Communication of a curious appearance lately observed upon the Moon. the Rev. Fearon Fallows. In a letter addressed to John Barrow, Esq. F. R. S

Abstract

Dear Sir, Cape Town, Cape of Good Hope, December 13,1821. I take the earliest opportunity of communicating to you a curious appearance which I lately observed upon the moon. My present means of making observations of this kind are indeed very limited, as the large telescopes, destined for the Cape Observatory, have not yet arrived. Still, however, it is right to have phenomena of this kind recorded, though the description may, from the want of proper instruments, be imperfect. About eight o’clock in the evening of the 28th of Novem­ber last, the sky being extremely clear, and the moon shin­ing with a brilliancy which I never observed in England, my attention was drawn to a whitish spot on the dark part of the moon’s limb, sufficiently luminous to be seen with the naked eye. Lest I might be mistaken, I requested Mr. Fayror, the assistant astronomer, to look at the moon attentively, and inform me whether he could observe any bright appearance upon the dark part of it. We both agreed in the identity of the spot, and remarked that now and then it seemed to flash with considerable lustre. Mr. Fayror having in his posses­sion a good achromatic telescope, which Mr. Troughton had given him previous to our departure from England, I requested the loan of it for a few nights, so that I might be able to exa­mine this appearance more minutely. Having directed the telescope to the moon, I immediately recognised the luminous spot, which seemed like a star of the sixth magnitude, and three others much smaller, but one of these more brilliant than the one we had seen with the naked eye. The largest spot was surrounded by a nebulous appearance. I could not per­ceive any thing of the kind about the small brilliant spot. The two others were similar to faint nebulae, increasing in intensity towards the middle, but without any defined lumi­nous point. As I am not yet in possession of a micrometer, by means of which the situation of these spots might be ascertained, you must rest satisfied with this imperfect de­scription. On the evening of the 29th, the sky being equally favourable for observation as on the former one, I found that the large spot was, at the least, as bright as before, two others were nearly invisible, and the small brilliant spot had disappeared. I was unable to make any farther observations, as a strong south-east wind began to blow with great violence on the goth, accompanied with rain, and which lasted several days. I wait with great anxiety for the next new moon, when, if the sky be clear, I shall not fail to examine it as carefully as my means at present will permit.