FORESTS AND RAINFALL,’ 193 
2. Wooded mountains have also an influence, much more 
important than that of bare mountains, on atmospheric precipita- 
tion, through their action in damping and chilling the layers of 
air which arise from them. ‘The extreme dryness of Spain, for 
example, in June, July, and August, is due to the fact that, 
though damp winds blow over it from the Atlantic, the mountains 
against which they strike, being bare for the most part, are heated 
by the sun, and the wind, instead of being chilled by contact with 
them, 1s warmed. ‘This is noticeable in the provinces of Grenada, 
Jaen, and Murcie, in spite of their proximity to the sea and the 
absence of more western chains of mountains which might 
intercept the damp winds. When rain does fall on the Sierra 
Nevada and the Sierra de Segura, disastrous floods are fre- 
quently the result, the ground being bare and calcined, and 
presenting no obstacle to the downrush of the water. The 
winds in the south of Europe blow generally from the west in 
summer, but for want of a refrigerator, such as plain or mountain 
woods, they do not get chilled and condensed. The rainfall 
is generally determined by accidents of relief; and, notably in 
Spain and Algeria, the wind which comes directly from the sea 
has a temperature much lower than that from the land, and 
becomes warmer, not colder, as it reaches the high plateaux. 
There is only one method of compelling these winds to cool 
and condense into rain, and this method, an zfallible one if 
foresters and aeronauts are to be believed, is forestation. All 
circumstances being equal, zooded mountains induce more 
abundant precipitation than bare mountains. But so far no 
conclusive experiments have been made except with forests of 
the plains. 
R. C. Mossman, F.R.S.E., F.R.Met.Soc., 
Honorary Consulting Meteorologist to the Society. 
