Cirro-stratus

Abstract

A RATHER perfect example of one variety of this cloud was seen here in the afternoon of September 27. A rapid fall of the barometer until 5 A.M., accompanied by a high wind, had been followed by a steady rise, the wind moderating some hours later. At 2 p.m., with a westerly light air, the sheet of cirrostratus which overspread the sky appeared in the form of a series of very perfect undulations, stretching nearly north and south. These were about fourteen in number, crowded together towards the east. The lower surface of the sheet was sharply defined, and could be followed with ease in its successive rise and fall. The cloud-filaments could be also traced, preserving their perpendicularity to the wave-fronts and conforming to the undulations of the lower surface with a closeness which I had not before observed, although sheets of cirro-stratus are common here. The whole system was drifting slowly to the east.