150 LIFE OF A TREE. 
that would easily freeze, remains uninjured, and it 
is found that only the young shoots are generally 
frozen through, even in the severest frost. Surely, 
then, the tree must have some source of warmth 
which can enable it to resist the cold of a winter’s 
night, and all the long frosts of that season too! 
This may be very prettily shewn also in the 
following simple manner. On a frosty day in 
Spring, take a small piece of ice and lay it on the 
bud of any tree which is just beginning to wake 
from the Winter’s sleep, and place a similar piece 
of ice ona piece of wood, close by the tree, so 
that both pieces are in the same condition as to 
external temperature. It will now be found that 
the piece of ice on the bud will slowly melt away, 
while that on the piece of wood remains unmelted. 
Evidently, therefore, the tree is warmer than the 
dead wood. Some experiments on this much 
neglected subject, have shewn the interesting fact 
that the tree is actually three or four degrees 
of the thermometer warmer than the air sur- 
rounding it. 
M. de Saussure noticed the curious fact that 
snow melts more quickly around the trunk of 
living than around that of dead trees,—a circum- 
