Light Air, Soot and Fog Cause 'Sky Darkness'"
From The Indianapolis Star, Wednesday, February 2, 1921: A cold “sky blanket of darkness” draped over Indianapolis for most of yesterday. The mysterious phenomenon, created by minute moist particles of soft coal soot suspended in the light air and deepened by fog, required the city’s businesses to use artificial light and automobiles were seen with headlights burning through the “smoke screen.” John Armington, local meteorologist of the United States Weather Bureau, said, “The air yesterday was darkened by floating particles of soot from the smoke of soft coal furnaces of the city and the light air failing to carry off the saturated soot. Such a condition is liable to occur in any city as large as Indianapolis, and it does not indicate the coming of any heavy storm. It is the worst case of sky gloom I have ever seen.”
“Light Air, Soot and Fig Cause ‘Sky Darkness,'” The Indianapolis Star, 2 February 1921, p. 5:5