SPECIFIC HEAT. Lis 
then, trees maintain at all seasons a constant mean tempera- 
ture of 12° [= 54° Fahr.], it is easy to see why the air in con- 
tact with the forest must be warmer in winter, cooler in sum- 
mer, than in situations where it is deprived of that influence.”* 
Professor Henry says: “As a general deduction from chemi- 
eal and mechanical principles, we think no change of tempera- 
ture is ever produced where the actions belonging to one or 
both of these principles are not present. Hence, in midwinter, 
when all vegetable functions are dormant, we do not believe 
that any heat is developed by a tree, or that its interior differs 
in temperature from its exterior further than it is protected 
from the external air. The experiments which have been 
made on this point, we think, have been directed by a false 
analogy. During the active circulation of the sap and the pro- 
duction of new tissue, variations of temperature belonging ex- 
clusively to the plane may be observed; but it is inconsistent 
with general principles that heat should be generated where 
no change is taking place.” + 
There can be no doubt that moisture is given out by trees 
and evaporated in extremely cold winter weather, and unless 
new fluid were supplied from the roots by the exercise of 
some vital function, the tree would be exhausted of its juices 
before winter was over. But this is not observed to be the 
* Memoria sur Boschi della Lombardia, p. 45. 
The results of recent experiments by Becquerel do not accord with those 
obtained by Meguscher, and the former eminent physicist holds that ‘‘a tree 
is warmed in the air like any inert body.” At the same time he asserts, as a 
fact well ascertained by experiment, that ‘‘ vegetables possess in themselves 
the power of resisting extreme cold for a certain length of time, C 
and hence it is jelieved that there may exist in the organism of plants a Picios 
independent of the conduction of caloric, which resists a degree of cold above 
the freezing-point.” In a following page he cites observations made by 
Bugeaud, under the parallel of 58° N. L., between the months of November 
and June, during most of which time, of course, vegetable life was in its 
deepest lethargy. Bugeaud found that when the temperature of the air was 
—34°.60, that of a poplar was only at —29°.70, which certainly confirms 
the doctrine that trees exercise a certain internal resistance against cold. 
+ United States Patent Office Report for 1857, p. 504. 
