14 On the MOTION of 



COR. 6. As the afcent of the fap thus renders all the ftrata of 

 a tree eafily feparable j and as this is the cafe in the lower parts 

 of the tree, fo far as the fap has afcended, while thefe parts 

 remain firmly attached to one another in the upper parts of 

 the tree, to which the fap has not afcended j it is therefore 

 evident, though contrary to what is generally fuppofed, that 

 this phenomenon is occafioned by the fap in its afcent, and 

 not by any return of the fap downwards from the extremities 

 of the tree. 



COR. 7. As the ligneous circles, during the afcent of the fap, 

 do thus fubfift in a loofe and unconnected ftate, the felling 

 of timber, during that period, ought by all means to be 

 avoided. This period of the fap's afcent varies jconfiderably 

 in different trees. In the plane, it may be dated from the 

 25th of December to the 25th of March ; in the birch, from 

 the i ft of March to the 26th of April ; in the oak, from the 

 20th of March to the ift of June j and it would be of ufe, 

 were the period of the afcent of the fap afcertained in like 

 manner in the other foreft trees. The oaks, which are cut 

 for their bark in April and May, during the afcent of the fap, 

 afford a foft and perifhable timber, compared to thofe which are 

 cut in the depth of winter. And the fame is the cafe with all 

 the plane-trees cut in the months of January and February, com- 

 pared to thofe which are cut in the month of November. To 

 obtain timber in its greateft perfection, I believe it cannot be 

 cut too foon after the fall of the leaf, as it is then in its moft 

 faplefs ftate, and the ligneous circles more firmly compacted 

 than at any other feafon. 



MARCH 22. 



Thermometer, at noon, 45. ; at midnight, 40. 

 THE feven lower incifions bled as on the former day ; the eighth 

 was wet, but all the upper ones remained dry. 



OBS. 12. 



