i8 On the MOT ION of 



communicated to it from the root, but from the action of 

 heat. The fouth fide of the trunk was this day far more 

 confiderably heated than the north fide ; and therefore, in the 

 evening, we found it bleed on the fouth fide, at the height of 

 eight feet, when it refufed to bleed, at the height of fix feet, 

 on the north fide. 



MARCH 26. 



Thermometer, at noon, 39. ; at midnight, 36. 

 THE feventh incifion bled ; but the eighth and ninth were 



dry, though they had bled the two former days. 



OBS. 19. On this day, and at all other times, whenever an in- 

 cifion bled on the trunk of the tree, all the incifions below it 

 bled likewife. 



OBS. 20. In the courfe of this experiment, we have found the 

 uppermoft incifion fometimes dry, though it had bled the day 

 before ; but here we find the two uppermoft incifions dry, 

 which had bled the two former days. The caufe is evident 

 from the thermometer, which this day flood lower than on 

 any of the preceding days of obfervation. 



AT this feafon, fo like is the fap in a tree, to the fluid in a ther- 

 mometer, and fo dependent in its motion on the heat and cold 

 of the atmofphere, that, by looking at the thermometer be- 

 fore I went abroad, I came now to guefs nearly the height at 

 which I mould find the tree bleeding. 



OBS. 21. The inverted branch D E bled this day plentifully at 

 E, though the two incifions below it refufed to bleed ; as did 

 alfo the branches below it, which were in their natural po- 

 fition. 



COR. 12. If at any time we woxild wifh to obtain a large quan- 

 tity of the fap of the birch, or of any other bleeding tree, it 

 would appear, therefore, to be a ufeful practice, to bend the 

 branches into a perpendicular pofition, and to cut them at 

 their extremities. 



COR. 13- 



