PARING AND BURNING. 289 



during the process of burning the bricks. This acid gas 

 being liberated, in the operation of burning soils, hastens 

 the formation of sulphates and salts. It divides the silicates, 

 and thus reduces them to a state in which the carbonic acid 

 of the air more easily decomposes them. If we go one step 

 further, and burn the vegetable matter of the soil, a portion 

 of geine is lost, and ashes are formed, whose operation has 

 been already considered (Chap. III.) They dissolve any 

 geine in soil ; hence the practice of burning the parings of a 

 peat meadow, whose ashes bring the balance into cultivation. 

 The whole practice of burning vegetable soil for its ashes is 

 wasteful. The original mode of paring and burning, and 

 which forty years ago was so common in Europe, is still 

 followed in many places in England, where the paring, from 

 the operation, is called push ploughing. It has been more 

 often given up, from the excessive crops it has produced, 

 exhausting the soil, than any inherent sin in the practice itself. 

 Instead of paring and burning,- it should rather be called 

 paring and roasting. The process should never go beyond 

 a good scorching. The effects of scorching insoluble geine 

 and inert vegetable fibre, may be illustrated by reference to 

 the effects of roasting coffee, or rye. A tough green berry, 

 or dry seed, which is quite insoluble, is made by this process 

 very soluble. Toasting bread has a like effect, and so has 

 baking on the dough. Though in roasting coffee, a large 

 portion of charcoal seems to be made, yet in the grounds of 

 coffee, vegetable fibre is in that state in which air and moist- 

 ure act, as they do on the geine of soils, converting the insol- 

 uble into soluble. If ever decided good effects have been 

 witnessed from the application of charcoal, independent of 

 rain water, they are due to the cause here pointed out. 



288. Turning in green crops is returning only to the soil, 

 the salts, silicates, and geine, which the plant has drawn out 



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