Vegetable Staticks. 119 



fpirations of trees, fhewn in the firft chapter) 

 that the fall of the fap, in thefe fap gages, 

 in the middle of the day, efpecially in the 

 warmer days, is owing to the then greater 

 perfpiration of the branches, which perfpi- 

 ration decreafes, as the heat decreafes to- 

 wards evening, and probably wholly ceafes 

 when the dews fall. 



But when towards the latter end oiAprll^ 

 the fpring advances, and many young moots 

 are come forth, and the furface of the Vine 

 is greatly increafed, and enlarged by the 

 expanfion of feverai leaves ; whereby the 

 perfpiration is much increafed, and the fap 

 more plentifully exhausted, it then ceafes to 

 flow in a vifible manner, till the return of 

 the following fpring. 



And as in the Vine, fo is the cafe the 

 fame in all the bleeding trees, which ceafe 

 bleeding as foon as the young leaves begin to 

 expand enough, to perfpire plentifully, and 

 to draw off the redundant fap. Thus the bark 

 of Oaks and many other trees moft eafily fe- 

 parates, while it is lubricated with plenty of 

 fap : But as foon as the leaves expand fuffici- 

 ently to perfpire off plenty of fap, the bark 

 will then no longer run (as they term it) but 

 adheres moft firmly to the wood. 



I 4 Ex- 



