VOL. IV."] PHILOSOPHICAL TRANSACTIONS. 355 



birches, much abated the bleeding of the trees above tlie bared places, but did 

 not quite stop it. 



The sap not only ascends between bark and tree, and in the pricked circles 

 between the several coats of wood ; but also through the very body of the wood. 

 For several young birches being nimbly cut off at one blow with a sharp axe, 

 and white paper immediately held hard on the top of the remaining trunk, we 

 stuck down pins in all the points of the paper as they appeared wet: and at last, 

 when most of the paper became wet, taking it away, but leaving the pins 

 sticking, we found them without any order, some in the circles, and some in 

 the wood between. And to confirm this further, we caused the body of a tree 

 to be cut off aslope, and then cut the opposite side aslope likewise, till we 

 brought the top to a narrow edge ; ordering the matter so, that the whole edge 

 consisted of part of a coat of wood, and had nothing of a pricked circle in it, 

 notwithstanding which, the sap ascended to the very top of this edge, and 

 wetted a paper laid upon it. 



To find out the motion of the sap, whether it ascends only, or descends also ; 

 we bored a hole in a large birch, out of which a drop fell every 4th or 5th pulse. 

 Then about a hand's breadth just under the hole, we sawed into the body of the 

 tree, deeper than the hole : whereupon the bleeding diminished about one half; 

 and having sawed just above this hole to the same depth, the bleeding from the 

 hole quite ceased ; and from the sawed furrow below decreased about half: and it 

 continued bleeding a great while after at both the sawed furrows, the hole in 

 the middle remaining dry. We repeated this with similar success on a syca- 

 more. 



Some trees of the same kind and age bleed a great deal faster and sooner than 

 others ; but always old trees sooner and faster than young. 



A wound made before the sap rises, will bleed when it does rise. 



While making these experiments, the weather changed from warm to very- 

 cold ; whereupon the bleeding in the birches, which began to abate before, 

 quite ceased. But all the sycamore and walnut trees, we had wounded, bled 

 abundantly ; some of which before bled not at all, and those that did, did so 

 but slowly ; and so continued night and day, when it freezed so hard, that the 

 sap congealed as fast as it issued out. The cold remitting, the birches bled 

 afresh, the sycamores abated very much, and the walnut trees quite ceased. 



We pierced two sycamores on the north and south sides, and both of them 

 from equal incisions bled a great deal faster from the north sides than the south, 

 which agrees with the preceding experiment. 



We set several willows with the wrong ends downward, and cut off several 

 briars, that had taken root at the small ends. This 29th of May the willows 



YY 2 



