j'4 Vegetable Statkks, 
of a foot diameter j and circles being as the 
fquarcs of their diameters lo pounds + 2 
ounces, will in 21 days be evaporated from 
the hemifphere of 30 inches diameter, which 
the Sunflower’s root occupies : Which with 
the 29 pounds drawn otF by the Plant ia 
the fame time, makes 39 pounds, that is 9 
pounds and i out of every cubick foot of 
earth, the Plant’s roots occupying more than 
4 cubick feet 3 but this is a much greater de- 
gree of drynefs than the furface of the earth 
ever fuffers for 1 5 inches depth, even in the 
dryeft feafons in this country. 
In a long dry fcalon, therefore, efpecially 
within the Tropicks, we niuft have recourfe 
for fufficient moifture (to keep Plants and 
Trees alive) to the moift ftrata of earth, 
which lay next below that in which the 
roots arc. Now moift bodies always com- 
municate of their moifture to more dry 
adjoyning bodies 3 but this flow motion of 
the afeent of moifture is much accelerated 
by the Sun’s heat to confiderable depths in 
the earth, as is probable from the following 
20th experiment. 
Now 1 80 grains of Dew falling in one 
Bight, on a circle of a foot diameter, = 
ii3fquare 
