Thus, in the mighty hands of God, the air was undergoing a gradual purification, to fit it for the animals He intended to create; the polypi were extracting from the water all the carbonate of lime it was absorbing from the air and earth, and fixing it in the soil, to be of use in a hundred ways at some future time, while the vegetation growing in abundance extracted it from the air, and fixed its carbon in their leaves and substance generally; these vegetables, decaying and falling upon the surface of the earth, accumulated there for ages, and formed a carbonaceous matter which was afterwards changed by time and pressure into coal. The same thing (on a very much smaller scale) is taking place in the tropical forests of the present age; there the surface-soil is quite black, and consists of nothing but decayed leaves and wood for several feet in depth, but in the present time there are hosts of insects, every one of which feeds upon this vegetable matter, preventing to a great extent its accumulation, while in the former age there was nothing to destroy it when once deposited on the ground; so that the carbon of these forests of the secondary period, existing through perhaps tens of thousands of years, extracted from the air a sufficient quantity of vegetable carbonaceous matter to produce thick seams of coal, even when compressed by the superincumbent strata. These forests were subject from time to time to inroads of the sea produced by the before-mentioned causes, and thus it is found that the seams of coal are often buried by several hundred feet of sand, clay, shale, &c., above which the same growth recommenced to form a second strata of coal, and ages must have elapsed whilst each of the numerous seams which interstratify the "coal measures" were forming. This coal, preserved in the depths of the earth, now forms the greatest treasure of the mine, and ironstone (from which iron is procured) would be almost useless but for the occurrence of these two minerals together with limestone (used as a flux) in the same locality, and it is this fortunate circumstance which enables England to produce such vast quantities of iron at such a cheap rate. The quantity of coal consumed in the iron-smelting works and for fuel generally, is beyond what could have been imagined a generation or two back, being somewhere about 50,000,000 tons annually, the coal brought to London alone in 1856 being 1,271,800 tons, yet there is such a plentiful supply of this valuable fuel in Great Britain alone that, supposing the annual consumption to rise to 70,000,000, it would serve (according to computation) a thousand years. Who shall say from whence fuel will then be obtained? probably from some other source provided by the foreknowledge of God, as was shown in the formation of the coal itself; for who could have imagined, a thousand years ago, when England possessed such immense forests, and wood was the universal fuel, that