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MEMOIR OF 
double the depth. For from an hole, suppose of 
two inches depth, will issue near double the 
quantity of what proceeds from an hole of an 
inch depth. So from the same hole, if it be 
bored on to double the depth it had, will issue 
double the liquor that first did.” 
Another experiment was instituted for the far- 
ther proof of the sap’s ascent through the woody 
part of the tree. 
“To put it out of all doubt,” says Mr Ray, 
“ we took away, on one side of a birch tree, bark 
and wood to a considerable depth, and bored an 
hole into the tree where the piece was taken 
away, out of which hole it bled copiously, not- 
withstanding we prevented any other sap coming 
on the filter but what proceeded from the hole.” 
These results being made known to the public, 
induced a great number of inquiries, relating to 
the proportion of the sap to the branches ; the 
position of' the branches, erect or otherwise ; 
whether the sap flows from the tops when cut off, 
or from the end of the stalks only ; also relating 
to the flowing of the sap in different kinds of 
trees, and the effects of temperature on these 
phenomena, and how far they are regulated by 
the age of the tree. 
“ In order especially to ascertain whether the 
sap ascended only, or descended also, we bored 
a hole into a large birch, out of which a drop fell 
every fourth or fifth pulse. Then about a hand’s 
breath, just uuder the hole, we sawed into the 
body of the tree deeper than the hole, whereupon 
