As the value of a coal bed bears a very near relation to that
of its average product, it is easily to be understood that the
analysis of a selected sample may be of very little utility. On
the other hand, the selection of a true average sample of the
bed may often be a task of considerable difficulty.
  The determination of the proportion of sulfphur in coals has
been much neglected in this country; and where it has been
done the method generally used has been to oxidate the pow-
dered coal in strong nitric or nitro-hydrochloric acid. This
mode of analysis is not so perfect as fusion with a mixture of
nitre, carbonate of soda, and salt, &c., which always, when
properly managed, brings all the sulphur into the form of sol-
uble sulphate, in whatever state it may have existed in the
coal. This exhaustive mode was employed in all our estima-
tions of this substance, and hence the quantities obtained may
seem greater than are shown to exist in similar coals which
have been treated with the acids.
  As has now been extensively demonstrated, the sulphur in
coals is rarely all combined with iron as sulphide or bi-sul-
phide. Some frequently exists in a free or uncombined con-
dition, as is shown in an analysis described in the following
pages. Some of it is frequently in the form of lime sulphate.
  When it is recollected that vegetable matters, decomposing
in a solution of sulphates of lime, magnesia, iron, &c., reduce
these salts to sulphides, with the production of hydrogen sul-
phide in the case of the earthy 'salts, and when we reflect that
this gaseous compound, HS, is decomposed, with the depo-
sition of free sulphur, on contact with the air, we can easily
understand how most of our coals must contain not only
pyrites but free sulphur.
  In the thirty-four marls, marly shzales, sands, and silicious con-
ci-etions, which have been analyzed, we find a general preva-
lence of lime, fixed alkalies, phosphoric acid, sulphuric acid,
&c. Some of the marls and shales contain these in such con-
siderable proportions as to make them locally useful for the
amelioration of poor sandy land. Some of these find an ap-
plication as mineral paint, for which they are adapted by their
I ro



CHEMICAL REPORT.



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