THE CHEMISTRY OF BOG RECLAMATION. 161 



other parts of Ireland as prejudicial to the interests of 

 the landlord. 



We shall now proceed to the philosophy of these pro- 

 cesses. 



First, the drainage. Everybody in Ireland knows that 

 the bog holds water like a sponge, and in such quantities 

 that ordinary vegetation is rotted by the excess of moisture. 

 There is good reason to believe that the ancient forests, 

 which once occupied the sites of most of the Irish bogs, 

 were in some cases destroyed by the rotting of their stems 

 and roots in the excess of vegetable soil formed by genera- 

 tions upon generations of fallen leaves, which, in a humid 

 climate like that of Ireland, could never become drained or 

 air-dried. 



But this is not all. There is rotting and rotting. When 

 the rotting of vegetable matter goes on under certain con- 

 ditions it is highly favorable to the growth of other vegeta- 

 tion, even of the vegetation of the same kind of plants as 

 those supplying the rotting material. Thus, rotten and 

 rotting straw is a good manure for wheat; and the modern 

 scientific vine-grower carefully places the dressing of his 

 vines about their roots, in order that they may rot, and 

 supply the necessary salts for future growth. The same 

 applies generally; rotting cabbage-leaves supply the best 

 of manure for cabbages; rotting rhubarb-leaves for rhubarb; 

 rose-leaves for rose-trees; and so on throughout the vegeta- 

 ble kingdom. 



Why, then, should the bog-rotting be so exceptionally 

 malignant? As I am not aware that any answer has been 



fiven to this question, I will venture upon one of my own. 

 t appears to be mainly due to the excess of moisture pre- 

 venting that slow combustion of vegetable carbon which 

 occurs wherever vegetable matter is heaped together and 

 slightly moistened. We see this going on in steaming dung- 

 hills; in hayricks that have been stacked when imperfectly 

 dried; in the spontaneous combustion of damp cotton in 

 the holds of ships, and in factories where cotton-waste has 

 been carelessly heaped; and in cucumber-frames and the 

 other " hot-beds" of the gardener. 



In ordinary soils this combustion goes on more slowly, 



