AS COMPARED WITH AN UNWOODED. 1 1 



We have abundant authority to prove that the belief in the 

 material influences which a wooded district exerts upon the rainfall, 

 and in the equally appreciable effects, though in a diametrically 

 opposite direction, which are caused by excessive denudation of 

 woodlands, exists in the minds of philosophers of acknowledged 

 enlightenment in our own country. For example, Sir John Herschel, 

 arguing that to a very great extent the climate of a country is under 

 man's control, states — "It is chiefly in his clearance or allowance 

 of arborescent vegetation, and in his artificial drainage of the soil 

 that his influence is perceptible." * And again, in his report to 

 the Meeting of the British Association in 1865, "On the rainfall 

 of the British Isles," t Mr Symons asserts that the annual mean 

 rainfall is decreasing appreciably upon an average of nearly 4 

 per cent, over the whole area of the country, but especially along a 

 tract of land extending from Cornwall to the Wash ; and this defi- 

 ciency he attributes partly to the extensive clearances of timber, and 

 partly also to the divergence of the flow of the springs by ground 

 drainage, now considered so necessary for the high-farming of the 

 present day, by the advanced agricultural knowledge of the period. 



If then it be true, that the overfelling of timber and the excessive 

 drainage of our fields tend to diminish the rainfall, and if a certain 

 quantity of rain at certain seasons be requisite to maintain the 

 equilibrium of healthy climate, and to prevent the recurrence of 

 periodic droughts, and short crops, whether root or cereal, it is 

 then clearly essential that there should be an adequate extent of 

 wooded surface properly distributed over the area of the country. 

 The main questions then come to be, Is it true 1 And next, What 

 would, for Great Britain, be an adequate and properly distributed 

 acreage of woodland 1 



As, however, it may be held that as yet the proposition is not 

 proved to be true that in this country the presence of a certain 

 counterbalancing proportion of plantation is requisite to maintain a 

 certain proportion of rainfall over the whole area, it may be as well to 

 defer meanwhile following out this branch of the subject in detail, 

 and we shall, therefore, at present only remark, that taking the total 

 acreage of Great Britain at 57,600,000 acres, of which probably 

 about 2,600,000 are under plantation and woodland, or barely 1£ 

 per cent, we find an amount which, if we except the relative 

 proportion of wooded lands in Portugal, is considerably under that 



* Familiar Lectures on Scientific Subjects. Weather and Weather Prophets. 

 t Proceedings of British Association, 1865. 



