COMPARATIVE COLDNESS OF LOW AND ELEVATED LOCALITIES, 37 
valleys, as well in the soil as by the constant exhalations of the streams that usually 
flow through them, increases both the density and the coldness of the atmosphere, 
and renders the occurrence of frost more likely. 
Several striking proofs of this position were presented to our observation during 
the last season. It will be remembered that in the month of September a frost 
occurred which, in most places near London, destroyed the Dahlias then in flower. 
Those gardens, especially, which lie in the vicinity of the Thames, had all their 
tender ornaments killed. We noticed at Chiswick some fine collections of Dahlias 
most completely mutilated. At Ealing Park, however, the seat of Mrs. Lawrence, 
which is situated on a much higher level, none of the Dahlias appeared to be injured. 
Those at Chatsworth, again, growing in a valley watered by a moderate sized river, 
were greatly damaged, and their flowers entirely cut off for the season ; while, on 
the exposed moors near Sheffield, where the cold seemed much more intense on 
account of the keen winds which prevail, we saw Dahlias and Roses blooming for 
nearly a month afterwards in uninterrupted vigour. 
We bring forward these simple cases, not, as already hinted, to support a new 
principle, but to establish and add force to one which is far from being properly 
considered. It has been clearly shown that an exotic plant which, perhaps, is as 
susceptible of injury as any other at present cultivated, and is, therefore, an 
excellent test of the temperature of any locality, suffers much more and sooner in a 
comparatively protected vale than at a greater altitude which is utterly unsheltered. 
The notion of placing plants in a low spot, to provide them with a natural screen 
from the wintry winds, must, consequently, be altogether abandoned. 
To the person anxious to acclimatize exotic plants, whether he be choosing a 
fresh residence, or selecting a spot in his domain suitable for the purpose, we recom- 
mend reflection on the foregoing remarks. Yearly experience attests, that while 
specimens planted on the sloping surface of hills sustain unharmed almost any 
degree of frost, those assigned to a low level are ever more or less frozen. It should 
be recollected that the majority of the plants which we strive to naturalize are from 
the elevated parts of tropical or warm countries, and are very rarely, or in only a few 
instances, found in the plains of more temperate regions. Such a consideration is 
peculiarly instructive. 
In the first place, it impresses us with the fact that they are mostly beyond the 
reach of the moisture evaporated from large bodies of water. Secondly, it proves 
that the soil in which they grow is not very deep^ and particularly tvell drained. 
And, lastly, it demonstrates that, from their position, the action of the sun and wind 
must perpetually preserve them from too rank a luxuriance, and effectually ripen 
their newly developed wood. 
The beautiful Himalayan and Mexican species of Pinus, and other trees and 
shrubs from the same or similar districts, will never, we are satisfied, have their 
hardihood fairly determined, until they are placed above the immediate influence of 
rivers or lakes, and on a slope that in some measure approximates to their native 
