[SPECIMEN OF BARK FROM A NOVA SCOTIA COAL MINE.]
With regard to this vegetation, it would imply the existence of sunlight, though some of the lower orders would require but little. The atmosphere was still dense and loaded with vapor. The lower orders of flowerless plants were succeeded by tree-like ferns, some of which grew to the enormous hight of forty or fifty feet. The careful observer will frequently find traces of this early vegetation in the lumps of common coal. Sometimes the galleries of coal mines are overhung with beautiful proportions of extinct vegetable forms. Thus a wise Providence has preserved the remains of primeval vegetation for perhaps millions of years, to tell us the story of those ancient forests, and reveal to us the various steps of creation. "The vegetation of the coal period presents a remarkable character, being composed almost entirely of the highest class of flowerless plants, along with a few of the lowest class of those that flower." (Dawson's Chain of Life, p. 96.)
Concerning the climatic condition of the earth during the coal-forming, (carboniferous) period, as it is called, the description given by Hugh Miller, the eminent geologist, may not be out of place: "From the circumstance that no dew is deposited in our Summer evenings, save under a clear sky, it is now ascertained that even a thin covering of cloud—serving as a robe to keep the earth warm—prevents the surface heat of the planet from radiating into the space beyond. And such a cloud, thick and continuous, as must have wrapped round the earth, as with a mantle, during the earlier geologic periods, would have served to retard, for many ages, the radiation, and consequently the reduction, of that internal heat of which it was itself a consequence. Nor would a planet, covered over for ages with a thick screen of vapor, be a novelty yet in the universe. It is doubtful whether astronomers have ever yet looked on the face of Mercury. It is, at least, very generally held that, hitherto, only his clouds have been seen. Even Jupiter, though it is thought his mountains have been occasionally detected raising their peaks through openings in his cloudy atmosphere, is known chiefly by the dark, shifting bands that, flecking his surface in the line of his trade-winds, belong not to his body, but to his thick, dark covering. Nor, yet further, would a warm, steaming atmosphere, muffled in clouds, have been unfavorable to a rank, flowerless vegetation like that of the coal measures.
"There are moist, mild, cloudy days of Spring and early Summer, that rejoice the heart of the farmer, for he knows how conducive they are to the young growth on his fields. The coal measure climate would have consisted of an unbroken series of these, with, mayhap, a little more of cloud and moisture and a great deal more of heat. The earth would have been a vast greenhouse covered with smoked glass, and a vigorous, though, perhaps, a loosely-knit and faintly-colored, vegetation would have luxuriated under its shade. That the vegetable growth must have been great we can easily imagine when we consider the immense quantities of coal throughout the world. It is a remarkable circumstance that, from the equatorial regions up to Melville Island in the Arctic Ocean, where continual frost now prevails; and from Spitzbergen to the center of Africa, the remains of the plants of the coal measures are identically the same. There seems to have been then only one climate over the whole globe, caused, no doubt, by the internal heat of the earth. We should not forget that Moses puts the elevating of the land and the production of vegetation in the same geological period, viz., between the second and third day."
"And the evening and the morning were the third day." (Gen. i, 13.) Before this time there seems to have been no seasons; but, after that, God appointed the sun, moon and stars "to give light upon the earth, and to be for signs, and for seasons, and for days and for years." That the sun and stars had been created long before this, we have no reason to doubt. We may, therefore, correctly infer that they were then, for the first time, visible from the surface of the earth.
