( 258 ) 
times more Fluid than the Quantity of the Chyle which 
enters into a Man’s Vefiels j and that becaufe, as the 
vSap to Plants is lefs nutritive than Chyle to Man, it 
mud be more in Qijantity. To fuck in the more 
^Sap, a Plant has a very great Surface, and thereby 
(Perfpiration promoting its imbibing of the Sap^ per- 
I'pires 17 times more than a Man in proportion to their 
refped-ive Weights. 
4. That a Man or a Plant may perfpire different 
Quantities, and yet continue in a healthy date. A 
Man may perfpire in 14 Hours from i-f ft to 3 ft j 
and a Plant, which at one time perfpir’d but 16 
Ounces, may without being lefs healthy, perfpire 
a 8 Ounces in the fame time. 
Mr. Hales obferv’d, that in order to fupply the 
Evaporation in the Leaves of a Vine, the Sap rofc 
151 Inches in 12 Hours, fuppofmg the Sap to rife 
as denfe as Water • but if it rifes in a Steam, which 
mud at lead be ic times rarer than Water, then 
the Velocity of the Sap will be 10 times greater, and 
confequently rife at the rate of Inches in an 
Hour. 
N. B. That the Heat of the Sun JhoulJ rarifie the ' 
Moifture of the Earth to that Degree^ or a great deal 
tnorey to drive it into the Roots of Vlants^ is very 
prohahle from feme Ohfervations that Mr, H. Beighton 
f. R.S. and my felf have made upon the Engine to 
raife Water hy Fire ; whereby it appears that the 
Steam or Vapour of heyltng Water is rarer than the 
Water from which it was produedy above i^qqo times ^ 
when its Elafliciiy is equal to that of common Air. 
Our Curious Experimenter, by his Obfervations 
upon II Evergreens, found, that they perfpire much 
lels than other Plants, and compares them to the 
exanguious Tribe of Animals ; whicti, as they perfpire 
little, 
