Site of the Ancient City of the Aurunci, 243 



By this addition to the theory, we advance, indeed, one 

 step towards the solution of the problem ; but there will still, 

 I conceive, be a difficulty in explaining other of the connected 

 phenomena : such, for example, as the generation of ammonia, 

 which so often is present amongst the products of a volcano ; 

 the evolution of air usually deprived of its oxygen, which bears 

 witness to the existence of some processes of oxidation going 

 on underneath ; and, above all, the escape of inflammable 

 gases, into which hydrogen enters as a constituent. 



With regard to the first of these facts, the generation of 

 ammonia cannot be disputed, although the amount formed 

 by volcanic action may still remain a matter of surmise. 



Those, however, who, with Baron Liebig, deny that gase- 

 ous nitrogen is capable, on the surface of the earth, of form- 

 ing any direct combination with hydrogen,* may be less in- 

 clined to condemn the hypothesis, with reference to this 

 subject, which I have thrown out in a former publication,*)", 

 and which assumes, that the quantity so formed was once 

 very considerable, as it traces to volcanic processes carried 

 on in the interior of the globe all the ammonia which would 

 be requisite for supplying the first plants with the nitrogen 

 they must have contained ; just as others have imagined all 

 the carbon necessary for the primeval vegetation to have 

 been derived from carbonic acid arising from the same in- 

 ternal source. 



At least, however, even those who refuse to go with me up 

 to this point, will admit, on the faith of the evidence which 

 I have adduced, the second fact noticed, namely, the extrica- 

 tion of nitrogen gas, either pure, or with a small admixture 

 of oxygen, from thermal springs in general ; since, amongst 



* In confirmation of this, it may be stated, that I have vainly attempted to 

 form ammonia by decomposing water in an atmosphere of nitrogen gas, through 

 the agency of a metal like potassium. Yet these two elements unite readily 

 when both are in a nascent state, as in the common experiment of producing 

 ammonia by the action of diluted nitric acid on powdered tin. Hence it may 

 be inferred, that, under a high pressure, such as may exist in the interior of 

 the globe, a union between these two elements would take place. 



t Three Lectures on Agriculture, page 97. 



