which contain, Ammonia. 44 1 



and sold as old woollen rags. Bones of all kinds, not ex- 

 cepting human bones, are sent by sea in great quantity 

 from this metropolis into the North ; many hundred tons of 

 these are ground, or rather broken small, in mills contrived 

 on purpose, as the quantity necessary for an acre of land is 

 small in comparison of other materials. The convenience 

 of c\tsy carriage is the cause of the most distant lands being 

 brought into the richest cultivation, It would not be pro- 

 per, on this occasion, to enter into a theoretical disquisition 

 on the nourishment of vegetables, whether they derive their 

 food wholly, or only in small "part, from the earth by their 

 roots, or from the atmosphere by their leaves and green parts j 

 but it appears clear to me, that that principle which the 

 farmers term warmth and force, is constantly accompanied 

 by the chemic element mentioned. This stimulus of en- 

 couragement and force is of more consequence to the growth 

 and eventual vigour of annuals than of perennials, and par- 

 ticularly at the early periods immediately succeeding the ex- 

 penditure of this sure principle which nature has provided 

 in the seed. The putrefactive fermentation always gene- 

 rates ammonia; the earth imbibes the different miasmata, 

 and holds them in store for the use of plants ; to these 

 they impart health, strength, and, as may be said, ap- 

 petite. 



A great difference is observed by farmers in the qualities 

 of the manure of cattle, when fed on oil cake^r on hay; 

 it is supposed to be of four times the value in the first case. 

 The beneficial effects of sometimes mixing lime with arable 

 soil is easily explained in this way. The ammonia is always 

 to be recognised by its peculiar smell. As soon as newly 

 slacked lime is mixed up with the mould of a good soil, but 

 which is beginning to show signs of impoverishment, In this 

 case, the ammonia, which had formed a chemic combina- 

 tion with the fixed acids of the manure (formerly ploughed 

 in and fermented) is set at liberty. These are the phospho- 

 ric and vitriolic acids, which, as i.s well known, will leave 

 ammonia to combine with lime. I have therefore no hesi- 

 tation in declaring, as matter of opinion, that the production 



of 



