Circular Rainbow seen from a Hill-top

Abstract

READING Mr. Fleming's letter in your issue of January 31 (p. 310), I am moved to put on record an observation of my own involving shadows and rainbows upon a cloud. On August 19, 1878, I was encamped upon a plateau known as Table Cliff, in the southern part of Utah Territory. The plateau has its longer dimension north and south, and ends southward in an acute promontory, precipitous toward the south, west, and east. The altitude is about 10,000 feet. On that day the air was moist, and scattering clouds were to be seen both in the valley beneath and in the sky above. A strong wind blew from the west. On that side of the promontory the air was clear; but at the crest a cloud was formed, so that the view eastward was completely cut off. This phenomenon is not unusual on mountain summits, and has been plausibly explained as due to the sudden rarefaction of the air on the lee-side of an obstacle. Standing on the verge of the cliff just before sunset, I saw my own shadow and that of the cliff distinctly outlined on the cloud. The figure appeared to be about fifty feet distant, and was not colossal. About the head was a bright halo with a diameter several times greater than the head. Its colours included only a portion of the rainbow series, but I neglected to record them, and do not venture to recite from memory. At the usual angle outside there appeared two rainbows of great brilliancy, likewise concentric with the head. They did not describe complete circles, but terminated at the left and beneath, where they met the shadow of the cliff. I estimated that 225° of arc were displayed. The phenomenon was continuous for some hours, the cloud-mass being persistent in position, notwithstanding the fact that its particles had a velocity of twenty-five or thirty miles an hour.