406 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



Water does not (as once supposed), exist in chemical combina- 

 tion with atmospheric gases, but in a state of steam. " It has 

 been shown, long since, that the amount of steam existing in a 

 given space and temperature, is the same whether that space be 

 free from, or filled with air." The aqueous vapor of the air con- 

 stitutes a distinct and independent atmosphere, the elastic force 

 of which forms, at difierent temperatures, different proportions 

 of the elastic force of the whole. 



For example, at the temperature of 66° it gives to the air 

 1.50th of its elasticity. A volume of air or gas, at any tempera- 

 ture, saturated with moisture, contains as much steam as would 

 exist, at the same temperature, in a vacuum of the same extent. 



The insensible vapor in the air is merely mechanically mixed 

 with the atmospheric gases, there is no chemical combination. 

 A diifusion of water, in a state of steam, by evaporation from the 

 earth's surface is seldom interrupted, continues often when the 

 rain is falling or ground covered with snow, under a burning sun 

 or in eternal ice fields. 



Evaporation continues in heat or cold. Snow, or a block of ice, 

 when the weather is intensely cold, will diminish under the action 

 of the air, without the least signs of liquefaction on the surface. 



The inference is, that the same quantity of vapor is formed 

 from snow and ice as would be evaporated from water, if water 

 could exist as a fluid below the freezing temperature. 



Plants of all kinds exhale moisture largely ; the transpiration 

 of plants increases progressively from March to August, and after 

 that time declines. A cabbage, under favorable circumstances, 

 has been found to emit, daily, water equal to its own weight. 



Such are the sources of the vast fountains of vapor which 

 replenish the atmosphere with water, for distribution, laden with 

 ammonia, in clouds, in dew-drops and in rain. 



Thus the relations of earth, sea, air and atmosphere may be 

 considered as a great fabric for the dispersion of light and heat ; 

 upon its proper working depends the wellbeing of all the animal 

 and vegetable kingdoms, its movements are not left to chance, 

 but are guided by harmonious laws, perfect and eternal. 



Mr. Solon Robinson said he had several interesting letters from 

 cori-espondents in the country ; one of them communicated copies 

 from Che London Times and Bell's Weekly Messenger, in relation 

 to the pt-tato disease, and giving Professor Bohlman's discovery. 

 Both remeujgg ^j-g ^^^jj authenticated ; remedy No. 1 was taken 



