86 LIFE OF A TREE. 
light reaches only their topmost boughs. The 
brittle Wainscot Oak of the Black Forest is 
produced by the same species as that which 
produces the tough and solid naval timber of 
Great Britain: but while the one is _ pro- 
duced in half-obscurity, the other stands often 
alone, enjoying the fresh light and air of our 
broad fields. 
If this is true, it may be said,—Then plants 
would grow best of all if exposed to perpetual 
sunlight. But this would not be the case. 
It appears probable that no created being can 
do without a certain amount of repose, and 
plants among the rest. Their nightly cessation 
from toil is as necessary to their health as 
their daily amount of labour also is. Hence 
where, as at the Poles, a continual shining of 
the sun exists for a certain space of time in 
the year, vegetation does not thrive under it 
as it does in the regions where regular succes- 
sions of day and night occur; and not a tree 
is to be found in all those dreary kingdoms 
of frost. 
From the hundred thousand chimneys of the 
great metropolis, every winter’s day, there proceed 
