228 THE CHEMISTRY OF CREATIOX. 



priate manures. Minute though the quantity 

 of ammonia present in the air may be, by a 

 slow process of this kind, it is extracted, 

 and the first shower causes it to be brought 

 into solution in a form in which it is readily 

 appropriated by the roots of plants.* The 

 Chinese, those original and practised agri- 

 culturists, says Sir J. F. Davis, will often pull 

 down the plaster of their kitchens, deeming the 

 trouble, labour, and expense of replacing it, 

 amply repaid by the rich stock of manure ob- 

 tained in the old plaster. It has been supposed 

 that the old plaster contains ammonia, and that 

 we have in this proceeding the artificial appli- 

 cation of a pripciple which, in nature, is in con- 

 stant operation on a larger scale; but the 

 quantities of ammonia absorbed are smaller. 

 A recent writer in the Paris Horticultural 

 Review mentions the following curious par- 

 ticulars illustrative of the value of powdered 

 charcoal as a manure : " About a year ago I 

 made a bargain for a rose-bush of magnificent 

 growth, and full of buds. I waited for them to 

 blow, and expected roses worthy of such a noble 

 plant, and of the praises bestowed upon it by 



* In addition to the ammonia obtained br plants from the 

 air, it appears that, according to the researches of Professor 

 Mulder, a slow process of formation of this substance takes 

 place in the soil during the putrefaction of bodies not contain- 

 ing nitrogen in their composition ; the nitrogen appearing to 

 be derived from that of the atmosphere. 



