This day's work differs from that of the preceding and succeeding days, in the fact that its sphere was without the earth, which was only indirectly influenced by it, and consequently the geological records give us no direct information upon the subject, though in two points they tally with the Mosaical account. In the first place, the deposits of coal, which preceded this period, indicate a time when a nearly uniform temperature, and that a high one, prevailed throughout the world. The coal beds are found not only in tropical regions, but in very high latitudes. Not only is the vegetation of which these coalfields are the result, analogous to that which is now found in warm climates only--(this might be the case, and yet we should not be justified in drawing the inference that the actual species of plants were tropical, for it often happens that different species of the same genus, having considerable external resemblance, are very different in their habits, some requiring tropical heat, while others flourish only in temperate climates)--but the marked feature is the astonishing luxuriance of this vegetation, which could only have been developed under the most favourable circumstances of warmth and moisture. Now the heat which any particular portion of the earth's surface receives from the sun depends entirely upon the latitude. hence it is impossible that a uniform high temperature could exist in a world which derived its heat wholly or chiefly from that source. Whether the high temperature which prevailed on the earth during the deposition of the coal measures was derived from internal heat it is impossible to say; it is evident that the temperature of the earth's surface has been in past times, and perhaps is now, modified by causes which no scientific research has been enabled to detect [Footnote: Since the sun's secular motion has been known, astronomers have suggested that the solar system has been carried through portions of space having variable temperatures. Geologists, however, do not seem inclined to accept this as a sufficient reason for the phenomena observed.]. But we may safely conclude that during the third day the earth did not derive its heat from the sun. The second point, the barrenness of the geological records of this period, will be noticed hereafter. The record of the fourth day's work admits of two interpretations, it may describe things merely as they appeared, or as they actually occurred.