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buried in the earth, is said to undergo 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 experiment did not succeed with 
Bucquet. But, whether the experiment succeeded to the extent 
described by Lemery, or not, is by no means essential to the in- 
quiry, since it is sufficient for our purpose, that, when the expe- 
riment is made on a very small scale, the mixture heats and swells, 
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 por- 
tion of sulphur, and becomes sulphuretted hydrogen gas. Admitting 
that, in neither of these instances, an union of the two simple sub- 
stances, the metal and the sulphur, is proved to take place ; still, I 
trust, these experiments shew that a saline combination 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 
