The METALS exist in the rocks, generally some distance down in the earth’s interior. Their amount, in some instances, is very great indeed. The only one which is rarely met with on our globe, and then in small grains, is the NATIVE IRON, _i.e._ iron in its _pure_ state. This want, however, could not have been recognized if we had not happened to find the substance in question in those blocks of meteoric iron, and in the small meteoric stones which have, from time to time, fallen to the surface of the earth during atmospheric storms, and, probably, owing to astronomical disturbances. For, of the iron, in its mixed conditions of different ores, we have an abundant supply. It is a singular fact, that the _native gold_, both in pure grains or flakes, and in solid “nuggets,” appears now to be the more prevalent form of that ponderous and imperishable substance. The ranges of quartz-rock in many chains of mountains are certainly thickly sown with seeds and nodules of fine gold. I may mention here, as an interesting circumstance to mineralogists and collectors of fossil pebbles, that the “native iron,” which is so scarce on the surface of the ground, is met with, from time to time, along with _manganese_, in the heart of siliceous pebbles. But I have never seen it where there is not the presence of some animal organism. Now all these _solids_, gold, iron, chalk, coal, salt—and I select incongruous items on purpose—are as truly portions of the earth’s mass as are the granite and slate, the sandstones and clays. And _so are also_ the flowing waters and the suspended clouds; and _so are also_ the component elements of these—oxygen, hydrogen, and the rest. It is, all of it, MATTER; it all obeys the law of gravitation, and it needs just as much to be taken into account, in a geological scheme or system, as the upheaving of granite rocks, the flux of lavas, or the icthyolite beds amidst the semi-crystalline ranges of the Old Red Sandstone formation. Consequently I have found, as has partly I trust been shown in the preceding pages, that even to handle and pronounce upon a pebble, such an one as we can pick up on the sea-shore any summer’s day, _all these elements_ must be taken into the account. In a “moss-agate,” for instance, I discover— _First._ A sandy cuticle, which we will rub off, as it is like the dust on your drawing-room table, a real thing, but out of place. _Secondly._ Siliceous matter. _Thirdly._ A purer form of this in chalcedony. _Fourthly._ The “moss,” which is a metal proper, tinged by _oxidation_. [N.B. Here is oxygen inside a pebble!] _Fifthly._ The whole or a part of some extinct animal’s petrified structure. _Sixthly._ One thing more, _sometimes_ a drop of water. _Seventhly and lastly._ Air, permeating the stone in fine pores and channels, one of the largest of which was in some cases a breathing-hole used by the zoophyte before he drew his last gasp.