VEGETABLE MOULD. 363 



except the process of decay. Diamonds cannot be 

 produced by the action of fire, for a high temperature 

 and the presence of oxygen gas, would call into 

 play their combustibility. But there is the greatest 

 reason to believe that they are formed in the humid 

 way, that is, in a liquid, and the process of decay is 

 the only cause to which their formation can with 

 probability be ascribed. 



Amber, fossil resin, and the acids in mellite, are 

 the products of vegetable matter which has suffered 

 decomposition. They are found in wood or brown 

 coal, and have evidently proceeded from the decom- 

 position of substances which were contained in quite 

 a different form in the living plants. They are all 

 distinguished by the proportionally small quantity 

 of hydrogen which they contain. The acid from 

 mellite (mellitic acid) contains precisely the same 

 proportions of carbon and oxygen as that from 

 amber (succinic acid); they differ only in the pro- 

 portion of their hydrogen. M. Bromeis* found, that 

 succinic acid might be artificially formed by the 

 action of nitric acid on stearic acid, a true process 

 of eremacausis ; the experiment was made in this 

 laboratory (Giessen). 



CHAPTER XL 



VEGETABLE MOULD. 



The term vegetable mould, in its general significa- 

 tion, is applied to a mixture of disintegrated miner- 

 als, with the remains of animal and vegetable sub- 

 stances. It may be considered as earth in which 

 humus is contained in a state of decomposition. Its 

 action upon the air has been fully investigated by 

 Ingenhouss and De Saussure. 



When moist vegetable mould is placed in a vessel 



* Liebig's Annalen, Band xxxiv., heft 3. 



