ATMOSPHERIC EXPERIMENTS. 
275 
with a calm deep-rooted conviction implanted in the 
boy, and increased by years of notice and experience. 
I have followed her footsteps, though far, very far dis- 
tant, as an humble admirer of perfection, nor can my 
veneration cease whilst reason continues undisturbed. 
Sept. 8th, 1828.— A remarkably dry and exhausting 
day, not from any peculiar influence of the solar heat, 
but from the arid state of the air, which was very dis- 
tressing to our feelings, and all tender vegetation be- 
came languid and suffering under its influence. I en- 
deavored 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 par- 
ticular states of the atmosphere. A linen cloth twelve 
inches square, which had absorbed an ounce avoirdu- 
pois 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 de- 
gree 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 evaporation from an 
acre of moist land covered with vegetation would ex- 
ceed 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 very accurate data can be drawn from this 
experiment ; for different soils will give out their mois- 
ture more or less easily, and succulent vegetables be 
