MANURES. 65 



But, besides the consideration of getting so lit- 

 tle, and that little of such equivocal character and 

 use, what do we lose by the process ? If we ap- 

 proach these little kilns, we find them emitting a 

 black smoke, which cannot be entirely consumed ; 

 and our eyes and noses are assailed by some stim- 

 ulating and ammoniacal matter, which is fast es- 

 caping, and which so far alters the atmospheric 

 air in the neighbourhood as to render it difficult of 

 respiration. Need we add that this is the animal, 

 oily, and gaseous matter essential to the vegetable, 

 and highly, important to vegetation T It may be 

 that the ashes obtained may give one or two good 

 crops of turnips; but even the advocates of this 

 practice admit that, " it ruins the land for an age ; 

 and hence it is that in England, tenants are restrain- 

 ed from paring and burning, especially towards the 

 close of their lease."* 



Clay burning is a different operation, and made 

 with different views ; not for the production of ash- 

 es or salts, which may operate chymically, but 

 merely (by the application of heat) to alter the tex- 

 ture of the soil ; to give to it an artificial division 

 and porosity ; to render what was cold warm, what 

 was wet dry, and what was compact granular. 

 But a small degree of heat will not produce these 

 effects; for, unlike the stems and roots of plants, 

 clay is not itself combustible ; and, to bring it to the 

 brick state, the heat applied must be long, contin- 

 ued, and great : hence it follows, that the practice 

 becomes objectionable on the score of expense, and 

 the more so as burned clay has no possible advan- 

 tage over the much cheaper substances of sand, 

 gravel, and pounded limestone. The operation of 

 all is merely mechanical, and exactly in proportion 

 to the quantity used. 



Our partiality for green crops ploughed into the 



* See Cobbett, part second, p. 168, " Year's Residence in the 

 United States.'' 



