316 ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 



RANGE OF TEMPERATURE AT GREAT HEIGHTS. 



Observations by mountaineers on the Andes and in the Himalayas 

 have shown that the difference between night and day temperatures, at 

 heights about 20,000 feet and over, is extraordinarily great, and that 

 changes are very sudden. The interposition of a cloud of ashes from 

 a volcano produced on Chimborazo a fall from 50° to 15° F. in two 

 hours. The effect of the shadows of clouds on the air and clouds below 

 must be very considerable. 



ELECTRICITY AT HIGH ALTITUDES. 



Electricity is highly developed in the upper regions. The observa- 

 tions carried on for some years at Pikes Peak, Colo., 14,132 feet above 

 the sea, and about 8,000 feet above the plain, proved that snow and hail 

 are always accompanied by electric manifestations. That St. Elmo's 

 fire, or the brush discharge, occurs when the air is damp with rain, 

 snow, or hail, and that the sparks are often almost continuous in storms 

 of snow and hail, the flakes and hailstones being highly electrified. 



The appearance of cirrus suggests the shaping of this cloud by elec- 

 trical forces, and there can be no doubt that the air above 5 or 6 miles 

 is strongly charged with electricity, which has not yet been experimen- 

 tally accounted for. The origin is generally attributed to evaporation, 

 by which the evaporated water and the water surface take electricities 

 of different signs, and there is some, but not sufficient, experimental 

 ground for the hypothesis. Gases consist of a vast number of mole- 

 cules which may be considered as separated from each other, and these 

 can receive an electric charge in such a manner as to make the whole 

 mass of a gas so charged electric. The minute particles of water float- 

 ing in the air, being better conductors, become more highly charged and 

 present comparatively smaller surfaces with a denser charge continu- 

 ally as they grow in size. In fine weather the air is usually positive, 

 in broken weather more often negative. The upper air is considered 

 to be positive and the earth's surface is negative. Electricity increases 

 very rapidly with height; thus Sir W. Thomson found the potential to 

 increase from 23 to 4G volts for a rise of 1 foot. Clouds in showery 

 weather are strongly electrified and the change of sign is often rapid. 

 In showers and thunderstorms streams of sparks run off from the end 

 of an elevated collecting wire, and sometimes from telegraph wires. 

 Valuable information for the forecast of storms and weather generally 

 might be obtained from observation of the electric character and 

 potential of clouds, obtained through instruments near the surface of 

 the earth. 



ATMOSPHERIC CURRENTS ABOVE 40,000 FEET. 



The observations of extraneous matter in the upper atmosphere after 

 the eruption of Krakatoa, showed that a current from east to west, of 

 hurricane force (80 miles an hour), nrevailed in August and September 



