78 REPORT — 1851, 



Report of the Committee appointed by the British Association to consider the 

 probable Effects in an (Economical and Physical Point of Vieto of the De- 

 struction of Tropical Forests. EyDv.HvGii Cleghorn, Madras 3Tedical 

 Estahlish7nent; Professor Forbes ^oyi,^, King' s College, London; Captain 

 R. Baird Smith, Bengal Engineers \ Captain 11. Strachey, Bengal 

 Engineers, 

 As preliminary to the Report which your Committee has now the honour to 

 submit, we have to make the following remarks. The great extent of the 

 subject prescribed to us, involving as it would have done, if completed in its 

 integrity, the collection of materials from every tropical region on the surface 

 of the globe, would have involved an amount of labour which we had neither 

 the time nor tlie means of devoting to the subject. Three of our members 

 had special duties required from them, which did not admit of being in any 

 way postponed*, and it has been consequently on the fourth (Dr. Hugh Cleg- 

 horn) that almost the entire labour has devolved of collecting and digesting 

 the materials now laid before youf. 



The personal relations of the whole of the members of your Committee 

 with the Tropical Region of British India, naturally suggested to them the 

 propriety of limiting their researches to that field wherein they had them- 

 selves been employed, and with the circumstances of vvhich they were not 

 only best acquainted, but had also the best means of filling in any imperfec- 

 tions which might exist in their knowledge. The subsequent report has 

 accordingly reference solely to the Forest Question as applied to India, and 

 we have endeavoured to collect all such information as would illustrate the 

 physical and ceconomical effects of the destruction of the natural woods, 

 which in that, as in other countrie's, are of such admitted importance. 



In reference to the physical efl^ects of the removal of forests, we found 

 considerable variety of opinions. There is, it must in fact be admitted, a 

 deficiency of exact or experimental information on ihe subject. Observations 

 of a, precise character on climate in countries once covered by forests but 

 now cleared, do not to our knowledge exist, and the evidence with which we 

 have to deal is a kind of evidence which admits of considerable variety of 

 interpretation. Of such evidence we have exhibited a number of examples, 

 and the general conclusions which appear to be warranted by these may be 

 perhaps best given in the following words of Humboldt, the most eminent 

 authority who has discussed the question : — 



" By felling trees which cover the tops and sides of mountains, men in 

 every climate prepare at once two calamities for future generations — the 



want of fuel, and the scarcity of water Plants exhale fluid from their 



leaves, in the first place, for their own benefit. But various important 

 secondary effects follow from this process. One of these is maintaining a 

 suitable portion of humidity in the air. Not only do they attract and con- 

 dense the moisture suspended in the air, and borne by the wind over the 

 earth's surface, which, falling from their leaves, keeps the ground below 

 moist and cool ; but they can, by means of their roots, pump it up from a 

 very considerable depth, and, raising it into the atmosphere, diflTuse it over 

 the face of the country. Trees, by the transpiration from their leaves, 

 surround themselves with an atmosphere, constantly cold and moist. They 



* Professor Royle has been engrossed with the Exhibition and his other duties. Capt. 

 Baird Smith has been employed on duty abroad, and Capt. Strachey was digesting his own 

 Himalayan researches for the press. 



t In drawing up the Report, it was necessary to alter and compress the language of the 

 original documents ; but care has been taken to give the opinions of the authors as nearly 

 in their own words as possible. — H. C. 



