JOHN P. NORTON'S ADDRESS. 573 



difficulties. The evaporation of water is its conversion into 

 vapor; during this conversion, a certain amount of heat is ab- 

 sorbed from the atmosphere and surrounding objects. You all 

 know that if you dip your finger into water, and hold it up, it 

 will feel cool, and particularly on the side from which the wind 

 blows ; it is possible to tell the direction of the wind in this 

 way, when all other means fail ; the reason is, that where there 

 is the most air, there is the most evaporation of the water, and 

 consequently a greater withdrawal of heat from the fingers. If 

 you take ether, or any fluid that evaporates much more readily 

 than water, you may obtain quite a degree of cold, even in the 

 hottest weather. It is, by means of some chemical substances 

 that evaporate very fast, possible to freeze water in a red hot 

 vessel. All that is necessary is to pour a substance that will 

 evaporate almost instantaneously, into the dish, and immedi- 

 ately afterwards a little water, from which the heat is all so 

 quickly withdrawn by the evaporation of the first liquid, that 

 it instantly becomes a solid mass of ice, capable of being turned 

 out and handled. This is a mere chemical trick, but it illus- 

 trates the great power of evaporation in producing cold. 



How must it be then, in spring, with two adjoining fields, 

 one of which is well dried, either artificially or naturally, and 

 the other saturated with water, because its constant level is but 

 a few inches beneath the surface. From the latter field a far 

 greater evaporation is constantly going forward, than from the 

 former, and it is consequently much colder ; the bulb of a 

 thermometer immersed in the soil of two such fields, will show 

 a difference of temperature ; a difference that must continue far 

 into the season. The sun's rays then, instead of warming the 

 earth, as they should do at this genial period of the year, are 

 mostly expended in evaporating a surplus of water; the field is 

 consequently backward and cold ; grass grown upon it is thin, 

 wiry, and sour; crops planted there come up straggling, yellow 

 and sickly. 



Thus much for the ill effects of this water in spring. It is 

 not difficult to explain why this same land resists drought so 

 poorly, although at first sight it seems a paradox that land, 

 which suffers in the early part of the season from too much 



