150 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



being equal, depends upon the existence of a temperature in 

 the interior which renders possible the processes of chemic- 

 al decomposition and combination, from which the luminous 

 body proper results. In ordinary cases the more or less cold 

 gases formed from the illuminating material rushing up from 

 beneath are heated sufficiently by the temperature developed 

 in the exterior zone of combustion to produce the change 

 necessary to luminosity. 35 C, IV., 1875, 220. 



INFLUENCE OF PKESSURE ON COMBUSTION. 



Some interesting observations have been made by Caille- 

 tet in burning different substances under pressure. He finds 

 that pressure slightly augments the temperature at which 

 combustion occurs, and that the luminous and actinic rays 

 emitted by the burning body are considerably intensified. 

 When a candle is made the subject of experiment, the base 

 of the flame, ordinarily bluish and transparent, becomes 

 white and very luminous. Soon, however, clouds of smoke 

 are formed, due to incomplete combustion. Under similar 

 circumstances the flame of phosphorus is not sensibly aug- 

 mented in brilliancy, but sulphur, potassium, alcohol, and 

 carbon disulphide burn much more vividly than in free air. 

 Annates de Chimie et de Physique^ Noveml)ei\ 1875. 



THE ABSORPTION OF SOLAR HEAT BY THE ATMOSPHERE. 



The discussions of the observations of the black-bulb-in- 

 vacuum thermometer, made in England during the past five 

 years, have led Mr. Stowe to the following conclusions in ref- 

 erence to the influence on solar radiation of the aqueous va- 

 por in the atmosphere. First, when the tension of vapor 

 is small, the radiation is greater than the average. Second, 

 the north and northwest winds, which contain little vapor, 

 show a Q^reater intensity of solar radiation than the south and 

 southeast winds. Third, the hourly changes, due to the va- 

 rying altitude of the sun above the horizon, are well marked, 

 and allow the approximate determination of the solar radia- 

 tion as unaffected by the absorption in the atmosphere ; this 

 latter varying from a minimum of ten per cent, to a maxi- 

 mum of twenty per cent. A change in the elevation of the 

 station, from 470 up to 1800 feet, diminishes the absorption 

 by five per cent. 7 C, II., 57. 



