192 A. G. HAMILTON. 
The injury done by the alteration of surface caused by settle- 
ment is then: first, Actual destruction of forests on the land 
affected ; second, the alteration of surface drainage which renders 
the plants adjacent to the altered area more or less unhealthy, 
the water being carried off that formerly lay in the ground and 
supplied moisture to the roots, and the plants being affected by 
the exposure of their roots to heat, cold and winds. 
(c.) Indirect injury caused by the alteration of climate effected by 
; clearing. 
Whether rainfall is affected by deforesting is a very vexed © 
question among scientific men, and an imposing array of authori- 
ties may be marshalled on either side. It is hard to come to any 
definite conclusion on the subject, for meteorological observations, 
except in one or two instances, have scarcely been long enough 
accumulated. 
Trees are said to temper climate and to increase rainfall. For 
example: “ With regard to the influence of forests on rain and 
snow-fall, there is as yet only a single series of observations sup- 
plying comparative statistics, and extending over a sufliciently 
long period. ‘These were taken in the neighbourhood of Nancy, 
and they show an important influence of forests on rain in the 
climate of Central Europe in increasing the rainfall. It might 
appear that the effects of forest on rain in the climate of Central 
Europe in winter would be small, for the difference between the 
temperature and humidity of the forests and open air is very little, 
and the quantity of moisture in the atmosphere is small. But 
the observations show that it is at this time of the year that forests 
get much more rain. This the writer attributes to the clouds 
being lower, the resistance which the forest offers to the movement 
of the air, and the moist west wind. Forests retain rain by the 
undergrowths of grass, moss, etc., much better than the open 
ground, and let water off superficially only after a heavy rainfall ; 
the moisture filters up slowly, and much of it is used for the 
evaporation of the trees.”* 
* Peterman’s Mittheilungen, quoted by E. Pollitzer in Sydney Quarterly 
Magazine, Vol, vit., p. 7. 
