the SAP in TREES. n 



MARCH 17. 



Thermometer, at noon, 44. ; at midnight, 42. 

 THE four lower incifions bled this day. The fifth, which had 

 bled on the two preceding days, was only moift. 

 COR. 3. When the thermometer falls to 44. the fap cannot run 

 at the fame height at which it ran when the thermometer was 

 at 47. 



OBS. 9. It was now obferved, and always found to be the cafe 

 afterwards, that each incifion bled fparingly at firft, and more 

 plentifully as the fap afcended higher. The moft copious flow 

 of the fap was always from the loweft incifions. When the 

 birch tree, therefore, is to be pierced, in order to procure a 

 large quantity of its fap, it will be found proper to make the 

 incifions as near the ground as poflible. 



MARCH 18. 

 Thermometer, at noon, 47. 3 at midnight, 42. 



THE five lower incifions bled, as on the former days ; but the 



fixth ftill continued dry. 



OBS. 10. The fap, by the temperature of the air, is capable of 

 remaining long ftationary. During the four laft days, it flood 

 nearly at the height of four feet, without afcending farther. 

 Ift another experiment, the fap continued ftationary for five 

 days, at the height of two feet, the thermometer, during that 

 time, never being above 43. at noon, nor above 36. at midnight. 



MARCH 19. 

 Thermometer, at noon, 48. ; at midnight, 41. 



Thermometer, at noon, in the fun, 65. 



THE fixth incifion did this day bleed for the firft time ; the fe- 

 venth was moift, and the reft dry. But though the incifions in 

 the trunk above the fixth, and fome that were made in the 

 branches, did not bleed ; yet they did all along gradually and 

 vifibly increafe in moifture. 



B 2 COR. 4, 



