170 SPECIFIC HEAT. 



physiognomj, but the individual trees have changed their habits, 

 conifers, which largely prevail in that climate, sending up shoots 

 from the roots as well as throwing them out lateraUj, and other- 

 wise approximating in growth to broad-leaved trees.* 



Specific Heat. 



Trees, considered as organisms, produce in themselves or in 

 the air, a certain amount of heat, by absorbing and condensing 

 atmospheric gases, and they exert an opposite influence by ab- 

 sorbing water and exhaling it in the form of vapor ; but there is 

 still another mode by which their living processes may warm the 

 air around them, independently of the thermometric effects of 

 condensation and evaporation. The vital heat of a dozen persons 

 raises the temperature of a room. If trees possess a specific tem- 

 perature of their own, an organic power of generating heat like 

 that with which the warm-blooded animals are gifted, though by 

 a different process, a certain amount of weight is to be ascribed 

 to this element in estimating the action of the forest upon atmos- 

 pheric temperature. 



Boussingault remarks : " In many flowers there has been ob- 

 served a very considerable evolution of heat at the approach of 

 fecundation. In certain arums the temperature rises to 40° or 

 50° Cent. [= 104° or 122° Fahr.] It is very probable that this 

 phenomenon is general, and varies only in the intensity with 

 which it is manifested." f 



If we suppose the fecundation of the flowers of forest trees to 

 be attended with a tenth only of this calorific power, they could 

 not fail to exert an important influence on the warmth of the 

 atmospheric strata in contact with them. 



Experiments by Meguscher, in Lombardy, led that observer to 

 conclude " that the wood of a living tree maintains a temperature 

 of -f 12° or 1Z° Cent. [= 54°, 56° Fahr.] when the tempera- 

 ture of the air stands at 3°, Y°, and 8° [= 37°, 46°, 4Y° F.] above 

 zero, and that the internal warmth of the tree does not rise and 

 fall in proportion to that of the atmosphere. So long as the lat- 

 ter is below 18° [= 67° Fahr.], that of the tree is always the 



* See note, p, 335-6, post. f Economie Burale, i., p. 22. 



