THE EARTH'S OCEAN OF VAPOR. 99 



Alexander von Humboldt, in his " Cosmos," * 

 thus refers to the vapor of the atmosphere, on 

 page 330, of vol. i. : 



" As the quantity of moisture in the atmosphere increases 

 with the temperature, this element, so important to the whole 

 organic creation, varies with the hour of the day, the season 

 of the year, and the degree of latitude and of elevation. Our 

 knowledge of the hygrometric relations of the atmosphere has 

 been materially augmented of late years by the method now 

 so generally and extensively employed of determining the 

 relative quantity of vapor, or the conditions of moisture of 

 the atmosphere, by means of the difference of the dew point 

 and of the temperature of the air, according to the ideas of 

 Daniell and of Dalton, and by the use of the wet-bulb ther- 

 mometer. Temperature, atmospheric pressure, and the di- 

 rection of the wind have all a most intimate relation to the 

 atmospheric moisture so essential to organic life. The influ- 

 ence, however, of humidity on organic life is less a con- 

 sequence of the quantity of vapor held in solution under 

 different zones than the nature and frequency of the aqueous 

 precipitations which refresh the ground in the form of dew, 

 mist, rain, or snow." 



* " Cosmos," vol. i., by Alexander von Humboldt. Lon- 

 don : Longman, Brown, Green & Longmans, 1849. Pp. 487. 



