Vegetable Staticks. 145 



to give its fap the rapid motion which was 

 neceflary for the blood of animals. 



In animals, it is the heart which fets the 

 blood in motion, and makes it continually 

 circulate; but in vegetables we can disco- 

 ver no other caufe of the fap's motion, but 

 the ftrong attraftion of the capillary fap- 

 veflels, affifted by the brisk undulations and 

 vibrations, caufed by the fun's warmth, 

 whereby the fap is carried up to the top of 

 the talleft trees, and is there perfpired off 

 thro' the leaves: But when the furface of 

 the tree is greatly diminifhed by the lofs of 

 its leaves, then alfo the perfpiration and 

 motion of the fap is proportionably dimi- 

 nifhed, as is plain from many of the fore- 

 going experiments : So that the afcending 

 velocity of the fap is principally accelerated 

 by the plentiful perfpiration of the leaves, 

 thereby making room for the fine capillary 

 veflels to exert their vaftly attracting power, 

 which perfpiration is effected by the brisk 

 rarefying vibrations of warmth : A power 

 that does not feem to be any ways well 

 adapted to make the fap defcend from 

 the tops of vegetables by different veflels 

 to the root. 



If 



