from the all-devourer, oxygen, and enters into innumerable uses. As the inflammable ingredient of wood, of bituminous coal, of petroleum and other vegetable and animal oils, we have it sealed up by Providence, as it were, for a temporary and portable fuel, pending the full development of man's proper authority over the elements—temporary, for it has long been a source of anxiety to economists that the resources of forests and coal-fields are so finite and their prospect of exhaustion so definite. It is evident from the coal "measures" that man was never intended to remain dependent on what he could pick up ready made for his needs, in respect of fuel any more than of other things; albeit this provisional supply for his infancy was made ample and accessible above all others. Even the novel service of carbon (which we shall observe more particularly further on) in smelting hydrogen "ore" from the vast mines of lake and ocean—as it does also the oxides of other metals from telluric mines—bids fair to be divided with some more unlimited artificial agency in due time. To the present time carbon, diffused and heated to intense brilliancy in burning hydrogen, has been our only artificial illuminant on a practical scale. And yet it now seems likely enough to be superseded in this office also, at no distant day, by fixed illuminators excited by the combustion of hydrogen or the force of electricity.
The better hydrogen becomes known, therefore, the more interesting and important to us it is found beyond all other elements, oxygen scarce excepted. To all the vital and delightful uses of water, as we have seen, it adds also those of light and heat. For, although scarcely luminous in itself, hydrogen is a principal source of the heat which makes other substances luminous, and is thus a chief condition of illumination. Terrestrial flame is generally hydrogen gas in the act of combustion, colored and made brilliant with white-hot carbon also oxidizing. Carbon may therefore be called a diffused illuminant, and the only one of any importance available at a living temperature, although in the terrific conflagration of the sun all things, even the most stable, are diffused in gaseous incandescence. The more stable substances that maintain their solid form in the comparatively moderate terrestrial heat of burning hydrogen until they become intensely bright are called fixed illuminators. Progressive examples may be cited: in platinum, the most non-fusible of metals, which endures and emits in light the intensity of hydrogen burning in air; and in lime, a still more refractory substance, which glows with dazzling power in the fierce combustion of hydrogen with pure oxygen, commonly known under the name of calcium light.
If Mr. Lockyer should succeed in verifying his startling hypothesis that hydrogen may be in fact the only thing in the material universe—not the water-parent only, but the all-parent—our present celebration of this great element would prove neither inopportune nor inordinate!
