304: METEOROLOGY. [Feb. 



temperature of the tree is intimately connected with the volume of 

 the trunk or branches, and with variations in the thermometric 

 conditions of the air. And the effects of temperature of this and of 

 the sunshine propagate themselves transversely, while the tempera- 

 ture of the ground is propagated from below upwards. The direct 

 comparison of the temperatures of the trees in the first two cases 

 being excluded, this determined the naturalists Boehm and 

 Breitenlohner to adopt the third method possible, that is, equal 

 lieights and equal depths. The two birch trees selected presented 

 the following measurements : — 



Horizontal distance between the two trees, . . 55 metres. 



Height of birch experimented on, ... 15'5 



Height of birch of verification or comparison, . 18 



Distance of lowest point of observation from ground, 6'3 



Distance of middle point from lowest, ... 6 



Distance of highest point from middle one, . . 6 



The tables on the preceding page are tabulated results obtained, 

 omitting remarks made on each, and on many of the details of each. 



Temperature [probably Centigrade] of the air around the trees. 

 Medias of fifteen daily observations from 21st August to 10th 

 September : — 



Trees. Points. 



Lower. Middle. Higher. Meditis. 



Experiment, .... 18-30 18-58 18-49 18-46 



Comparison, .... 18-30 18-50 18-38 18-39 



Difference, 0-08 0-11 007 



Temperature of the trees from 21st August to 10 th September. 

 Average of fifteen daily observations : — 



Trees. Points. 



Lower. Middle. Higher. 



Experiment, 16-68 16-83 17-57 



Comparison, 17-03 16-88 17-13 



Difference, +0-35 +0-05 -0-44 



Thermometric difference between the air and the tree : — 



Trecs. Points. 



Lower. Middle. Higher. 



Experiment, -1-62 -1-75 -0-92 



Comparison, —1-27 --1-62 -1-25 



In a comparison of the two trees, it is seen that the comparison 

 birch is in its lower part as much hotter, as in its upper part it is 

 as much cooler than the tree which was the subject of experiment. 

 The higher temperature of the lower part of the former is attribut- 

 able to the greater accumulation of heat in its greater volume ; and 

 on the other hand, that in the upper part is -smaller through the 

 greater diameter retarding the occurrence of the extremes. 



The writer of the paper onh'- gives his initials, A. S. 



John C. Brown. 



