y chemical
compounds having a different composition, tends to prove that matter
consists of atoms the mere arrangement of which produces all the
properties of bodies. But when we find that a different arrangement
of the same elements gives rise to various physical and chemical
properties, and a similar arrangement of different elements produces
properties very much the same, may we not inquire whether some of
those bodies which we regard as elements may not be merely
modifications of the same substance?--whether they are not the same
matter in a different state of arrangement? We know in fact the
existence of iron in two states, so dissimilar, that in the one, it
is to the electric chain like platinum, and in the other it is like
zinc; so that powerful galvanic machines have been constructed of
this one metal.

Among the elements are several instances of remarkable similarity of
properties. Thus there is a strong resemblance between platinum and
iridium; bromine and iodine; iron, manganese, and magnesium; cobalt
and nickel; phosphorus and arsenic; but this resemblance consists
mainly in their forming isomorphous compounds in which these
elements exist in the same relative proportion. These compounds are
similar, because the atoms of which they are composed are arranged
in the same manner. The converse of this is also true: nitrate of
strontia becomes quite dissimilar to its common state if a certain
proportion of water is taken into its composition.

If we suppose selenium to be merely modified sulphur, and phosphorus
modified arsenic, how does it happen, we must inquire, that
sulphuric acid and selenic acid, phosphoric and arsenic acid,
respectively form compounds which it is impossible to distinguish by
their form and solubility? Were these merely isomeric, they ought to
exhibit properties quite dissimilar!

We have not, I believe, at present the remotest ground to suppose
that any one of those substances which chemists regard as elements
can be converted into another. Such a conversion, indeed, would
presuppose that the element was composed of two or more ingredients,
and was in fact not an element; and until the decomposition of these
bodies is accomplished, and their constituents discovered, all
pretensions to such conversions deserve no notice.

Dr. Brown of Edinburgh thought he had converted iron into rhodium,
and carbon or paracyanogen into silicon. His paper upon this subject
was published in the Transact