144 Vegetable Staiich . 
If the fap circulated, it muft needs have 
been feen defeending from the upper part 
of large gafhes cut in branches fet in wa- 
ter, and with columns of water prelling on 
their bottoms in long glafs tubes, in Expe- 
riment 43, and 44. In both which cafes, 
it is certain that great quantities of water 
paffed thro’ the ftem, fo that it muft needs 
have been feen defeending, if the return of 
the fap downwards were by trufion or pul- 
lion, whereby the blood in animals is re- 
turned thro* the veins to the heart : And 
that pulfion, if there were any, muft necef- 
farily be exerted with prodigious force, to 
be able to drive the fap thro' the finer capil- 
laries. So that if there be a return of the 
fap downwards, it muft be by attradion, 
and that a very powerful one, as we may 
fee by many of thefe Experiments, and par- 
ticularly by Experiment ii. But it is hard 
to conceive, what and where that power is 
which can be equivalent to that provifion 
nature has made for the afeent of the fap 
in confequence of the great perfpiration of 
the leaves. 
The inftances of the Jeffamine tree, and 
of the Paffion tree, have been looked up- 
on as ftrong proofs of the circulation of the 
4 fa?* 
