VOL. LXVIII.3 PHILOSOPHICAL TRANSACTIONS. 281 



mosphere at 43°, the tree at 45''. — Ex[}. 16. Nov. 10th, atmosphere at 49", the 

 tree at 55*^. — Exp. IJ . Nov. ]8th, atmosphere at 42°, the tree at 44°. — Exp. 

 IS. Nov. 20th, fine day, the atmosphere at 40°, the tree at 42°. — Exp. ig. 

 Dec. 2d, the atmosphere at 54°, the tree at 54°. 



In all these experiments, which were made at very different times in the day, 

 viz. in the morning, at noon, and in the evening, the tree was in some degree 

 warmer than the atmosphere, excepting in one, when their temperatures were 

 equal. For the sake of brevity I have drawn up my other experiments, which 

 were made on different trees, into 4 tables, as they were made at 4 different de- 

 grees of heat of the atmosphere, including those made in the time of the very 

 hard frost in the winter of 1775-6. They were as follows : 



1st. The Atmosphere at 29°. 



Names. 



Carol, poplar 2 



Engl, poplar 4- 



Orien. plane 3 



Occid. plane 3 



Carol, plane ! 



Birch 3 



Scotch fir 3 



Height. 

 Ft. In. 



6 

 6' 



Diam. 

 In. 



2 



n 



1| 



n 



Heat. 

 29i° 



2y| 



30 



30 



30 



29s 



28i 



Height. 

 Ft. In. 



Names. 



Cedar libanon 2 2 



Arbutus 2 6 



Arbor vitae ,2 8 



Dissid. Cyprus 3 



Lacker varnish 3 6 



Walnut tree 5 



Diam. 

 Ft. In. 

 4j 

 3| 

 Sh 

 2| 

 2 

 2 4 



Heit. 

 28i 

 30 

 29 

 30 

 30 

 31 



The old hole in the walnut-tree being full of sap was frozen up, but a fresh 

 one was made. 



2d. The Atmosphere at 27' 



Names. Height. Dta 



Ft. In. 



Spruce fir 4 



Scotch fir 1 5J 



Silver fir 3 1 1 



Weymouth fir + 6 



Yew 3 7 



Holly 2 6 



Plumb-tree 4 6 



Dead cedar 3 11 



Ground under snow .... 3 deep- 



2' 



u 



2A 



3 



2 



3 



3 



Heat. 

 32° 

 28 



30 



30 



30 



30 



31^ 



29 



3+ 



3d. The atmosphere at 24". 



Names. Heat. 



Spruce fir 23" 



Scotch fir 23 



Silver fir 23 



Weymouth fir 23 



Yew 22 



Holly 23 



Dead cedar 24 



The same trees we mentioned when the thermometer was at 29°, in new 

 holes made at the same height, and left some time pegged up till the heat pro- 

 duced by the gimlet was gone off; but in which, as they were moist from the 

 sap, the heat could be very little, especially as the gimlet was not in the least 

 heated by the operation. 



4th. Atmosphere 16". 



Car. poplar 170 Carol, plane 17" 



Eng. poplar 17 Birch 17 



Ori. plane 17 Scotch fir I6J 



Occ. plane 17 



The sap of the walnut-tree, which flowed out in great quantity, froze at 32°. 

 VOL. xiv. O o 



