ATMOSPHERIC EXPERIMENTS. 407 



under its influence. I endeavoured to ascertain 

 the power of absorption possessed by the air at 

 the time by an experiment, rude enough to be sure, 

 yet it tended in some measure to indicate the rapid 

 manner in which fluids are exhaled in particular 

 states of the atmosphere. A linen cloth twelve 

 inches square, which had absorbed an ounce avoir- 

 dupois of water, was suspended in the shade in a 

 free current of air, and in the course of ten minutes 

 it had lost 436 grains, equal to one-sixteenth of its 

 weight. This great evaporation was principally 

 effected by the absorbent power of the air, and 

 manifested in some degree the exhausting influence 

 that was passing over the earth and the vegetation 

 exposed to the current of air ; and as the roots 

 could not derive sufficient moisture from the soil 

 to supply what was thus drawn from the leaves, 

 the foliage became languid and flaccid in conse- 

 quence. The linen, containing the same quantity 

 of water, was then spread upon a short turf in the 

 sun, and in the space of ten minutes it lost 368 

 grains, and this was effected without any particular 

 influencing current of air ; accordingly, the evapo- 

 ration from an acre of moist land covered with 

 vegetation would exceed one hundred and twenty- 

 two cwt. of water in an hour ! As the quantity 

 drawn from the vegetation on the soil may be equal 

 to the shelter its foliage affords to the earth, no 



