ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 315 



on the capacity of the atmosphere for modifying and absorbing" the 

 radiant energy of the sun. 



An investigation of the principal elements concerned in arresting 

 and reflecting the sun's rays would yield results of much interest. The 

 absorptive and reflecting capacity of vapor in the free air has not been 

 determined. The power of any constituents of the air, e. g., ozone and 

 ammonia, apart from dust particles, to scatter the rays of light, is not 

 known. The reasons of the variations in radiation from the surface of 

 the earth on different days when the weather continues clear and appar- 

 ently unaltered have not been fully made out. Much information might 

 be gained by regular observation at two stations, one on the summit of 

 a high mountain and one on the plain below, of the radiation value by 

 day and night, and by comparing the results with the weather, humidity, 

 and any meteorological phenomena which might be connected with 

 them. Thus, for instance, a comparison of the radiation from the sta- 

 tions on two clear days, one dry and the other humid, would give some 

 idea of the effect of invisible vapor in arresting radiation. If true 

 vapor in a dry state is found in the laboratory not to stop heat rays, 

 the inference would have to be made that vapor in the air often exists 

 in a different but still invisible condition. 



WINDS AND TEMPERATURE AT GREAT HEIG-HTS. 



Balloon observations have shown that a variety of currents are often 

 met with in asceuding from the earth to 10,000 or 20,000 feet, and also 

 remarkable changes of temperature, not always in the direction of cold. 

 On September 15, 1805, the air near the earth was 82°, and at 23,000 

 feet was 15°. On July 27, 1850, after passing through a cloud fully 

 15,000 feet thick, 17.1° was noted at 19,685 feet, and —36.2° at 23,000 

 feet. On July 17, 1862, at 10,000 feet, 26°; at 15,000 feet, 31°; at 19,000 

 feet, 42°; then a little below this height only 16°. Thus it seems that 

 the air may be not seldom divided into adjacent masses differing by 

 26° or more. On March 21, 1863, up to 10,300 feet the wind was east, 

 between 10,300 and 15,400 feet, west; about 15,000 feet, northeast; 

 higher still, southwest, and from 20,600 to 23,000 feet, west. The 

 changes of humidity are also sudden and great. Bain falls sometimes 

 4,000 feet above falling snow, at 15,000 feet. At 37,000 feet the dryness 

 of the air indicated an "almost entire absence of vapor," yet cirri 

 floated high above this altitude. On July 27, 1850, the balloon passed 

 through about 7,000 feet of ice-cold water particles, and ice needles 

 formed only at — 10°. On March 21, 1893, a small balloon with regis- 

 tering apparatus was sent up to a height much greater than any of 

 which there was previous record, and a temperature of — 51° C. was 

 recorded at about 45,500 feet; the air at Vaugirard at the time being 

 at 17° O. This very promising experiment of sending recording bal- 

 loons to great altitudes seems likely to lead to valuable information on 

 the condition of the air up to 50,000 or 60,000 feet m various kinds of 

 weather. 



