796 On the Influence of Forests on Climate. [Aug. 



its oxygen to form carbonic acid at the expense of the carbon of the 

 vegetable, or by disengaging carbonic acid formed in various ways. 

 That the modifications which the atmosphere experiences when in 

 contact with growing mushrooms are the same day and night. That 

 if fresh mushrooms are placed in an atmosphere of pure oxygen, a 

 great part of that gas disappears at the end of a few hours. One por- 

 tion of oxygen which is absorbed combines with the carbon of the 

 plant to form carbonic acid, whilst another part appears to be fixed in 

 the vegetable, and to be replaced, at least in part, by nitrogen dis- 

 engaged by the mushroom. That when fresh mushrooms remain some 

 hours in an atmosphere of nitrogen, they modify but slightly the 

 nature of that gas. The sole effect produced is confined to the dis- 

 engagement of a small quantity of carbonic acid, and sometimes to the 

 absorption of a very small quantity of nitrogen." 



No application of human skill and labour tends so greatly to vary 

 the state of the habitable surface, as that employed in the drainage of 

 lakes and marches, since not only the localities of many animals and 

 plants, but the general climate of a district, may thus be modified. 

 There seems little doubt that in the United States the rapid " clear- 

 ing" of the country has rendered the winters less severe and the sum- 

 mers less hot, in other words the extreme temperatures of January and 

 July have been observed from year to year to approach somewhat 

 nearer to each other, and thus most probably, the mean temperature 

 has been raised. The same result has been brought about in this 

 country, only to a much greater extent. 



The entire destruction of all woods and forests has rendered India 

 liable to those dreadful calamities which always follow a deficiency of rain. 



The N. W. Provinces were denuded of their trees during the wars 

 that attended the decline and fall of the Muhammedan Empire, and 

 the rise and progress of the Jats, Seikhs and Mahrattas. These lawless 

 freebooters swept away all the groves from the face of every district 

 they invaded, whilst they never thought of renewing them, or encourag- 

 ing their renewal, in those countries which they permanently occupied ; 

 many fertile regions were thus turned into dreary and arid wastes. 



It is marvellous to think how slowly and reluctantly the Indian 

 Government has come forward and acknowledged the necessity for that 

 merciful provision of nature by which the thirsty soil is refreshed with 

 grateful drafts and rendered habitable by man. Trees perform as 



