the Chemical Theory of Volcanos. 23 



rated as to form a strong sulphurous water. The sulphate of 

 soda formerly contained in it had disappeared, and iron pyrites 

 was deposited. On the bottom of a mineral spring contain- 

 ing only a very small quantity of sulphate of soda, I once 

 found pieces of iron pyrites, including organic matters, such 

 as branches and stalks of plants. There is no doubt but this 

 iron pyrites was formed by the decomposition of sulphate of 

 soda and carbonate of the protoxide of iron, at the expense of 

 the organic matter. 



We can accordingly have no difficulty in admitting most 

 sulphurous springs to be formed in the same way. In support 

 of this, it may be mentioned, that all sulphurous springs con- 

 tain sulphates and organic matters. I allude only to those in 

 the Pyrenees, which, it is known, abound in vegetable matter, 

 the so-called Baregine. 



Many exhalations of sulphuretted hydrogen in volcanic dis- 

 tricts may be formed in the same way. At least organic 

 matters are not wanting in sedimentary rocks which have 

 been broken through by volcanic actions, and sulphates exist 

 in many volcanic products. 



Assuming that melted lava comes in contact with sulphur at 

 any part of a volcano, and that the so-called liver of sulphur is 

 produced from alkalies and alkaline earths ; supposing, farther, 

 that the liver of sulphur meets with water and carbonic acid 

 gas, sulphuretted hydrogen will be evolved. We may easily 

 imagine exhalations of this gas during the course of many 

 ages, when liver of sulphur abounds. Indeed, the immense dis- 

 engagements of carbonic acid gas in many districts of former 

 volcanic action, within the memory of man, appear to lend con- 

 siderable weight to the theory suggested. 



I shall not pass from these considerations without alluding 

 to Daubeny's supposition that the chlorine also, which we know 

 to be generally present in volcanos, may be united with the 

 hydrogen evolved by the decomposition of water. But the 

 occurrence of a considerable quantity of chlorine in a free 

 state in a volcano is hardly probable. We know this substance 

 to be merely evolved when a peroxide is present. In the inte- 

 rior of the earth there is only that of manganese which is 

 rather abundant. When present at the locality of a volcano, 



