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And observation and experiment indicate that the planets Saturn and Jupiter, very much larger than the earth, are not yet wholly freed from their nebulous surroundings; whence we conclude they are still in a heated state.

Moreover, since the difference in gravity is much less than the difference in size, it must be these larger planets are so much less dense, and therefore so much less advanced in a geological sense than the earth. They are relatively "younger," that is, less mature than the earth. Not but that their origin may have been as remote, indeed more remote, since they are farther from the sun, but that their greater volume makes the longer time necessary to reach the same condition.

While on the other hand our moon, very much smaller than the earth, is already cold, Present conthrough and through. A mere skeleton dition of the of a world, scarred with storms and gap

moon.

ing with craters of extinct volcanoes, but without any semblance of life.

That is what the earth is coming to by and by; destined not to burn up, but to freeze out.

This may be a startling conclusion; though, when we reflect how many thousands of years the earth has already been inhabited, and that the crust as yet may not exceed a hundred miles in thickness, and that it must thicken possibly to four

thousand miles before the internal fires are entirely out, it is clear there is no immediate occasion for alarm.

It will appear, then, that Mr. Hutton's statement quoted in the preceding lecture, that "Science finds no prospect of an end" of this world, was premature. It teaches us, on the contrary, that in the natural order of events an end must come at length to the existing order of things throughout the material universe. But it is not of the end but of the beginnings of the world we are especially to speak-the passing of this earth from the chaos and vacuity in which it began to a condition of order, harmony, usefulness, and life.

pearance.

And so we return from this digression to mark, in closing, the point in the development of our subject to which the present discussion carries us. The appearance of the sun is not yet reached. in the regular order of events. We have Epoch of the sun's ap- spoken of it here for the sake of unifying our discussion of light, but the event itself occurred at a later period. It was after the establishment of the firmament-after the gathering of the waters into the sea-after the first appearance of dry land probably, that the sun-light struggled through the vapors that surrounded the sun upon the one hand and shrouded the earth pon the other.

"Let there

be light."

Our present discussion takes us only to the first appearance of clear light, and that was not from the sun. The skilful chemist will show you now how, by the combination of certain simple elements, both light and heat may be produced. But this production was not dependent on man's invention or discovery. Far back in the line of ages, before there was a man upon the earth, aye before there was any solid earth or the sun in yonder heavens had begun to shine, the principle we now call chemical affinity, with gravitation and various forms of energy, were created and set at work; and out of the diffused and attenuated material that swung in chaos and disorder and black night, were gathering and assorting and combining the elements in due harmony and proportion. And in compliance with the divine plan, and in obedience to the fiat of the Eternal, "Let there be light," there was light.

III.

THE FIRMAMENT,

THE SEA AND DRY LAND.

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