Po J 
have been treated with the greateft 
attention, and have thrown much 
light upon this fubject. 
This celebrated author has taken 
a great deal of notice of thofe air 
bubbles. which cover the leaves 
-when plunged | under water. He 
fays, p. 26, that the leaves draw 
- thefe bubbles from the water. He 
_ is the more perfuaded that this is 
the cafe, becaufe he found thefe 
bubbles did not appear when the 
water had ‘been boiled fome time, 
a fish more ies the. Wa- 
“ing” in it. He "had ae “Obe ey 
‘that they did not appear after fun- 
fet. Page 31, he explaias ‘his opi- 
nion farther upon. this head: he 
_ fays, that thefe air bubbles are pro- 
‘duced by common air adhering to 
the external furface of the leaves, 
ey which 
