52 
SELECTED ARTICLES. 
ART. XII.— ON THE EFFECTS OF TERRESTRIAL RADIA- 
TION ON THE PROCESSES OF VEGETATION ; AND SOME 
ACCOUNT OF THE CHINESE METHOD OF PROPAGATING 
FRUIT TREES. By J. Murray. 
It has been shown that the cooling process of radiation, by 
which the temperature of the surface of the earth is lowered 
so considerably, differs materially on the inclination of the hill 
compared with the bosom of the valley. Mr. Daniell, indeed, 
states, on one occasion, a difference amounting to 30°: that is to 
say, the thermometer on the inclined surface maintained ahigher 
temperature by 30° than another placed on the horizontal or 
level plane of the adjoining valley. This difference is cer- 
tainly enormous; but it is proved beyond a doubt, that a slope, 
an inclined plane, for instance, radiates less by many degrees 
than the surface which is altogother horizontal. Indeed, I 
think we may collect abundant proof of this important fact 
among the mountains and the valleys of Italy. On the plains 
of Piedmont, the vines which are suffered to attain a consider- 
able altitude on lofty poles planted as their support, are de- 
tached from these poles towards the approach of winter and 
prostrated on the earth, where they are secured from injury 
by the straw. — This treatment protects them from the effects 
of the intense, though short winter which reigns on the plains 
of Piedmont; for even at Turin, the water in my room has 
been congealed into a solid mass of ice throughout its entire 
extent. The olive succeeds in Tuscany, but the almond, po- 
megranate, and plants of the Citrus family, flourish but imper- 
fectly; and yet on the acclivities of the amphitheatre of the 
Appennines, which forms a semicircle round the magnifi- 
cent city of Genoa, you find that the pomegranate, the lemon, 
and the orange, mature their fruit and luxuriate. Even the 
imperial city is indebted for the palm branches to the palms 
which succeed in the open air at Nice. Now, the only differ- 
ence in these circumstances consists in a reduction of the loss 
