A Shadow on the Sky

Abstract

I DO not know how common is the phenomenon described by Mrs. Charlotte Hall in NATURE of Nov. 9 (p. 25), but her communication leads me to report a much less striking appearance of the same kind, which I witnessed Feb. 20, 1870, in this neighbourhood. I was taking an early walk, and had mounted to the top of a ridge commanding an eastern view, about fifteen minutes after sunrise. The sky was veiled in a dark white. Above me, a little to the south and east, hung a ball of vapour in mid air, warmed into smoke-colour by the rays of the sun, and yet so dense as to cut off these rays, and cast a rectilinear shadow of dark blue against the white coat of the sky. The shadow was sharply defined, and the whole effect was not unlike the nucleus and tail of a comet. In a few moments the shadow faded out, and, shortly after, the ball itself was dispersed. The moon, in its third quarter, was visible somewhat past the zenith, and surrounded with vapour. Twelve hours later we had a violent rainstorm.