Wollaston, whom many of us know, and it is obtained in great purity
and beauty. It is a very remarkable metal in many points, besides its
known special uses. It usually comes to us in grains. Here is a very fine
specimen of native platinum in grains. Here is also a nugget or ingot, and
here are some small pieces gathered out of certain alluvial soils in
Brazil, Mexico, California, and the Uralian districts of Russia.

It is strange that this metal is almost always found associated with some
four or five other metals, most curious in their qualities and
characteristics. They are called platiniferous metals; and they have not
only the relation of being always found associated in this manner, but
they have other relations of a curious nature, which I shall point out to
you by a reference to one of the tables behind me. This substance is
always native--it is always in the metallic state; and the metals with
which it is found connected, and which are rarely found elsewhere, are
palladium, rhodium, iridium, osmium, and ruthenium. We have the names in
one of the tables arranged in two columns, representing, as you see, two
groups--platinum, iridium, and osmium constituting one group; and
ruthenium, rhodium, and palladium the other. Three of these have the
chemical equivalent of 98-1/2, and the others a chemical equivalent of
about half that number. Then the metals of one group have an extreme
specific gravity--platinum being, in fact, the lightest of the three, or
as light as the lightest. Osmium has a specific gravity of 21.4, and is
the heaviest body in nature; platinum is 21.15, and iridium the same; the
specific gravity of the other three being only about half that, namely,
11.3, 12.1, and 11.8. Then there is this curious relation, that palladium
and iridium are very much alike, so that you would scarcely know one from
the other, though one has only half the weight of the other, and only half
the equivalent power. So with iridium and rhodium, and osmium and
ruthenium, which are so closely allied that they make pairs, being
separated each from its own group. Then these metals are the most
infusible that we possess. Osmium is the most difficult to fuse: indeed, I
believe it never has been fused, while every other metal has. Ruthenium
comes next, iridium next, rhodium next, platinum next (so that it ranks
here as a pretty fusible metal, and yet we have been long accustomed to
speak of the infusibility of platinum), and next com