-1859] WRITINGS OF JOSEPH HENRY. 13 



doxical as it may seem, it would be warmer when it re- 

 turned to the lower level than when it left it. In ascending 

 to the top of the mountain it would deposit its moisture in 

 the form of water or snow, and the "latent heat" given out 

 from this, would increase the heat of the air; and when it 

 descended on the opposite side to the same level from which 

 it ascended, it would be warmer on account of this addi- 

 tional heat. The configuration of the surface of our con- 

 tinent has on this account therefore a marked influence on 

 the temperature of its different parts. 



3. The effect on its climate, of the position of a country, 

 as regards its proximity to the ocean, will be evident from 

 the facts relative to the radiation and absorption of heat by 

 different substances. All bodies on the surface of the earth 

 are constantly receiving and giving out heat. A piece of 

 ice exposed to the sun sends rays to this luminary, and re- 

 ceives in return a much greater amount. The power how- 

 ever of radiating and receiving heat is very variable in 

 different bodies. Water exposed to the same source of heat 

 receives and radiates in a given time far less than earth ; 

 consequently the land (especially in the higher latitudes) 

 during the long summer days or during the growing season, 

 receives much more heat than the corresponding waters of 

 the same latitude ; and though the radiation at night is 

 less from the water than the land, yet the accumulating in- 

 crease of temperature of the latter will be much greater 

 than that of the former. The reverse takes place in the 

 winter. While therefore the mean temperature of the ocean 

 and of the land in the same latitude may remain the same, 

 the tendency of the land is to receive the greater portion 

 of the heat of tlie whole year during the months of summer, 

 and thus, by a harmonious arrangement with respect to the 

 production of organic life, to increase the effect of the solar 

 radiation, and to widen the limits within which plants of a 

 peculiar character may be cultivated. 



Proximity to the sea however has another effect on the 

 climate, which depends upon the currents of the former, by 

 which the temperature of the earth due to the latitude is 



