82 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 sanre 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 under the hole, we sawed into the 

 body of the tree deeper than the hole, whereupon 



