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solutions of the metals, it has been found that a considerable pre- 
cipitate ensues ; and the precipitate thus made, is found to be com- 
pounded of the metal and the sulphur. The sulphuret thus pre- 
cipitated is black from silver, yellow from bismuth, brown from 
copper, &c. Thus also, in subterranean situations, similar effects 
ensue from the agency of the sulphuretted hydrogen on the solution 
of the metal. The action of a double affinity is exerted. The dis- 
solved and oxydated metal, as well as the sulphuretted hydrogen, 
suffers decomposition. The sulphuretted hydrogen being separated 
into its two constituent principles, hydrogen and sulphur, the former 
unites with the oxygen, which had oxydated the metal, and had 
contributed to its solution, abstracts it from the metal, and with it 
forms water ; whilst the latter principle, the sulphur, deserted by 
the hydrogen, combines with the metal, thus nearly freed of its 
oxygen, and reduced, and forms with it a sulphuret, which is 
precipitated. 
Iron, water, and sulphur, either now exist, or have left traces of 
their existence, in almost every subterranean situation ; and there is no 
difficulty to oppose the supposition, that, in such situations changes 
and combinations may have ensued, resembling those which we have 
just described. One material difference would, however, arise ; the 
sulphuretted hydrogen, prevented from escaping, must have pene- 
trated, and forcibly exerted its influence on, every particle of the 
metallic solution. This would also be acted on by the surrounding, 
as well as by the mingled, carbonaceous, and earthy or alkaline 
matter. The oxygenized sulphur and metal, thus acted on, at once, 
by these deoxidating powers, must each have given up the portion of 
oxygen attached to them; which, with the hydrogen, would form 
water; whilst the pure metal and sulphur, entering into intimate 
union, would form pyrites, possessing a metallic lustre. 
It is here proper to remark, that the very ingenious experiments 
of Mrs. Fulhame show clearly, the powerful influence of water, in 
