PROGRESS OF METEOROLOGY IN 1889. 229 



means of the heat which becomes latent during its evaporation. The 

 vessel containing the water was immersed in an ice calorimeter and was 

 connected with a large space, which could be rendered both vacuous 

 and dry. The water was then allowed to evaporate until the space was 

 filled with saturated vapor; the amount of heat requisite to produce 

 the observed, evaporation was determined from the amount of mercury 

 which was expelled from the calorimeter, and this then gave the amount 

 of water evaporated. One outcome of the experiments is that Gay- 

 Lussac's law holds good almost up to the temperature of saturation. 

 The mass of water that must be evaporated in order to saturate a 

 si)ace of 1 liter capacity at 0° C. was found to be -l.SSO milligrammes; 

 lience the specific volume of a(iueous vapor saturated at 0° C. is 204.7 

 liters, and its pressure is 4.02 millimeters. 



Spectrum of ozone. — Mr. W. K. Hartley has examined the absorption 

 spectrum of ozone by j^hotographing the ultra-violet rays transmitted 

 through measured quantities of the gas, and finds that it possesses 

 most extraordinary absorptive powers. Coruu's experimental proof 

 that the ultra-violet rays of the sun are absorbed with energy by the 

 atmosphere is attributed by Hartley to the ozone which is a constituent 

 of the atmosphere, and which he states is in greater proportion in the 

 upper regions than near the earth's surface. 



The explanation that the blue color of the sky is caused by reflection 

 from minute particles which on account of their size most readily reflect 

 blue rifys is rejected as incompetent, and a theory suggested by his 

 own experiments is presented. He announces that ozonized oxygen is 

 highly fluorescent, and that the color of the fluorescence is a beautiful 

 steel blue. Oxygen also is believed to be fluorescent, though this has 

 not been proved. 



He concludes (1) that the extreme limit of the solar spectrum ob- 

 served by (Jornu is caused by the gases in the atmosphere, probably 

 both by oxygen and ozone ; (2) that the blue of the sky is caused in 

 l)art by fluorescence, and probably ozone and oxygen are the chief 

 fluorescent substances ; (3) that ozone is generally present in the air in 

 sufficient quantity to render its characteristic absorption spectra visi- 

 ble, and that therefore it gives a blue color to the atmosphere by ab- 

 sorption. {Nature, xxxis, p. 475.) 



Specific heat of sea water. — Messrs. Thoulet and Chevalier have pre- 

 sented to the Paris Academy of Sciences the results of a series of 

 nieasurements on the specific heat of sea water at <liflerent degrees of 

 dilution and concentration. The results are applied to explaining the 

 enormous infiuence exercised by the sea in modifying climates. 



The law of thermal radiation. — H. F. Weber derives for the total 

 radiation of a body the formula 8= CFT^J where C is a constaiit de- 

 pending on the nature of the substance and the properties of its sur- 

 face, and a is a (constant for all solids. F is the radiating surface and 



