Extract of a letter from Captain Basil Hall, R. N. F. R. S. to William Hyde Wollaston, M. D. V. P. R. S. containing observations of a comet seen at Valparaiso

Abstract

The comet described in Captain Hall’s letter was visible for 33 days in the months of April and May, 1821. During the first week its nucleus was bright and distinct; but being then in the interior of the country, he did not commence observing it till the 8th of April, when its nucleus had become so indistinct as to render its measurement by the micrometer uncertain. On its first appearance, the comet appeared of a dull white, and its tail presented a dark streak between its sides, giving it the appearance of being split. On the second evening the tail subtended an angle of 7°, reaching to ρ Ceti; on the seventh the nucleus was less bright, and the tail shorter, arising, probably, from the increased distance of the comet. The tail was at first nearly at right angles to the horizon, but each succeeding night it inclined more to the south. Tables of the observations and some sketches of the appearance of this comet accompany Captain Hall’s communication.