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solutions of the metals, it has been found that a conside able pre- 

 cipitate ensues ; and the precipitate thus made, is found to be com- 

 pounded of the metal and the sulphur. The sulphuret thus preci- 

 pitated is black from silver, yellow from bismuth, brown fron, 

 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 oxidated the metal and had con- 

 tributed to its solution, abstracts it from the metal, and with it forms 

 water ; whilst the latter principle, the sulphur, deserted by the hy- 

 drogen, combines with the metal, thus nearly freed of its oxygen, 

 and reduced, and forms with it a sulphuret, which is precipi- 

 tated. 



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 

 penetrated, and .forcibly exerted its influence on, every particle of 

 the metallic solution. This would also be acted on by the sur- 

 rounding, 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 



