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moistened with water, and buried in the earth, is said to under- 

 go so considerable a degree of expansion, as to make the earth, 

 over it, heave and crack, in several places ; from which even fire is 

 said sometimes to burst. Fourcroy, indeed, states, that this expe- 

 riment did not succeed with Bucquet. But, whether the experi- 

 ment succeeded to the extent described by Lemery, or not, is by 

 no means essential to our inquiry, since it is sufficient for our pur- 

 pose, that, when the experiment is made on a very small scale, the 

 mixture heats and swejls, sulphuretted hydrogen escapes, and the 

 more fixed principles enter into intimate union. 



Perhaps neither of the above experiments affords an instance of 

 the union of the pure metal and sulphur : in the latter experiment 

 it seems obvious that this is not the case ; and in that related by 

 Dr. Thompson, it appears highly doubtful. Still an examination of 

 the changes which may be supposed to be effected, in these experi- 

 ments, will place the subject in a more clear point of view. The water 

 is undoubtedly decomposed ; its oxygen combines with the metal and 

 with the sulphur, forming a metallic oxide and the sulphuric acid ; 

 and these uniting, form a solution of the metal in the sulphuric 

 acid. The separated hydrogen attaches to itself in its nascent 

 state, a portion of sulphur, and becomes sulphuretted hydrogen gas. 

 Admitting that, in neither of these instances, an union of the two 

 simple substances, the metal and the sulphur, is proved to take 

 place ; still, I trust, these experiments show that a saline combina- 

 tion of these two bodies may be formed, in subterranean situations, 

 merely by the aid of water. This being ascertained, it remains to 

 discover, whether from this compound, and the other substances, 

 necessarily present, a metallic sulphuret is not likely to be formed. 



The changes which we are to contemplate, then, are those which 

 would take place in a saline metallic solution, exposed to the in- 

 fluence of sulphuretted hydrogen, and the surrounding carbona- 

 ceous substances. By the addition of sulphuretted hydrogen to ; 



