EXPERIMENTS on EVAPORATION. 121 
water, and placed as before, the evaporation in the fame 
time was exactly one inch. If this experiment may be 
fuppofed to reprefent the operations of nature, the con- 
clufion will be, that the evaporation from the furtace of 
the earth, is but little more than one third of what the 
evaporation is from the furface of water. 
EXPERIMEN ‘FE’ FV. 
Another thing I had in view was to know what the eva- 
poration was from plants and trees, In order to make an 
eftimate of this, Auguf? 20, I took up four different forts 
of plants, with as much of the earth adjoining to each as 
wholly covered their roots. Each plant; with the earth 
thus about it, being fix inches fquare, I put into a wooden 
box of the fame form and fize. The boxes were covered 
with thin lead, well cemented at the joints, that nothing 
might evaporate that way ; and had two apertures at the 
top; one, to admit the ftem of the plant, the other, that 
the plant might be fupplied with water, but which was 
kept ftopped when not in ufe. Having taken the weight 
of each, I placed them in the ground that they might have 
the fame degree of heat as before; leaving as much of the 
plant above the furface of the earth, as when it was in its 
natural ftate. In this fituation I added known quantities 
of water, aiming to put in from time to time as much as 
I thought they would throw off. At the end of thirty 
days { took them up, taking an account of their weight as 
before, and alfo that of each plant. The refult is expref- 
fed in the following particulars : 
The feveral forts Weight of the Water evaporat- 
_ of plants. plants. ed in 30 days. 
Grains, Grains. 
Appletreesi ty 23 er ie eel bey 
Alder tree. - - - 30 - - - = 2593 
Spearmint, - - - 22 - - = = 5186 
Clover, - - - - 43 - - = = 1894 
5 In 
