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in the science is much less considerable, but whose application of 
some recent discovery has happened to have been fortunate. Thus 
the opinions entertained by Dr. Hutton, and by Dr. Playfair, respect- 
ing the formation of pyrites, and the precipitation of pure metallic 
substances, I trust, will be no longer tenable, when compared with 
the ingenious experiments and observations of still more recent date. 
The union of metals with sulphur, without the aid of fire, is dis- 
coverable in many instances. A familiar instance is the violet tar- 
nish which attaches itself to polished silver; and which, being 
allowed to accumulate, will form a crust which may be separated by 
bending the silver, or striking it with a hammer. This pellicle has 
been examined by Mr. Proust, who asserts it to be a sulphuret of 
silver. The common sympathetic inks, formed of metallic solu- 
tions, the writing of which, before invisible, is immediately darkened 
by sulphuretted hydrogen, is also an instance of the union of metal 
and sulphur, in the moist way. So also is that kind of shining pel- 
licle which forms on wainscots, painted with white lead, and which 
have been exposed to the influence of sulphuretted hydrogen. 
An observation of Dr. Thompson, in his excellent System of Che- 
mistry, affords us very decided evidence on the question which we 
are about to discuss, which is. Whether the natural combinations 
of sulphur with the metals are effected, by means of fusion by heat, 
or by solution by water ? Speaking of a combination of sulphur with 
copper, he says, “ This compound may be formed by mixing copper 
filings and sulphur, and making them into a paste with water, or 
even by mixing them together, without any water, and allowing them 
to remain a sufficient time exposed to the air, as I have ascertained 
by experiment*.” This point is also illustrated by the well-known 
artificial earthquake of Lemery, in which a mixture of equal parts 
of iron filings and of sulphur, being moistened with water, and 
* A System of Chemistry, by Thomas Thompson, M.D. vol. i. p. 117. 
