stately river is floating off the land—not noisily, but sullenly and angrily, as if the waters had some great wrong to avenge upon the land. And all these filchings from the mountain and the plain are restored again to the sea. Old Ocean is receiving back his own. The rivers are his allies, and right faithfully do they forage to supply the cravings. of his insatiate maw.

We witness such work in progress during the brief moment of our tarry upon the earth. We look back along this line of operations, and discern for the first time the gigantic results which have already been achieved by the wearing agency of waters. Not during the lifetime of Adam's race alone, but during the age of quadrupeds which preceded him through the dynasty of reptiles, still more ancient, have these denuding forces been ceaselessly engaged in scraping, and gouging, and scarring the face of Nature. River-beds have been deeply excavated and again obliterated by a plethora of rubbish poured forward by some more gigantic operation. Lake basins have been. scooped out-Niagara gorges dug-square. miles of land, with its underlying rocky floors, have been swept away. From the summits of the Catskill Mountains the Old Red Sandstone once stretched eastward perhaps to Massachusetts Bay. The powers of water have strewn it over Long Island Sound, and far to the seaward of Sandy Hook. The Cumberland Table-land once reached a hundred and fifty miles westward over the basin of Middle Tennessee. The site whereon the city of Nashville now stands was once a thousand feet beneath the level of the land. Half a state was scraped away to extend the borders of Mississippi and Alabama. The Alleghanies, in their prime, were three thousand feet higher than human eyes have ever seen them. Their ancient summits are sunken in the Atlantic and the Gulf of Mexico. The Great American Desert was once as

fertile as the Valley of the Mississippi. A great river watered it for a thousand miles, while a hundred tributaries dispensed fertility throughout the region which was then the garden, as it is now the desert, of the continent. That fertile plateau has been drained to death. Each stream has drilled a frightful chasm deep through the rocky foundations of the plain (Fig. 96, 97). The mother stream, the Colorado, dwarfed to a withered mockery of what it was, now creeps along at the bottom of a narrow gorge whose rocky walls rise, in places, more than a mile in height. From the brink of this appalling chasm, three hundred miles in length, your vision struggles down six thousand feet into the realm of twilight; and in this prison the attenuated Colorado-patriarch of American riversis wasting its senile energies from year to year, but, with "the ruling passion strong in death," it is still carrying off the land, even though each season's work sinks it into a deeper grave.

Such are the works of running streams and corroding waves. The record of their labors is the utterance of the destiny of the land. History inverted becomes prophecy. The doom of the mountains is engraven upon their rocky buttresses. Half the pride of the Alleghanies has already been removed. Rounded hill-top is dissolving into plain. Defiant granite, which buffeted the lightnings that rent Sinai, and frowned upon the flood that drowned "the world," shall yet be brought down by the multitudinous pelting of rain, and the insidious sapping of frost. The mountains shall be wiped off. The continents shall be worn out. The rivers will have dug their graves. The ocean will have eaten up the land; and all there was of the dwelling-place of man will be a rocky islet, a ragged bluff, a sunken reef-the crumbs that fell from old Ocean's meal,

There was a time when, by degrees, the continents were

slowly and steadily surging from the sea. The sea,

robbed

of half his dominions, has ever since been raging around the borders of the land. At last he will again reclaim his own, and the universal empire will be Neptune's.

It is vain to hope that elevatory forces can permanently avert the disappearance of the land. We discover here another argument against the vague belief entertained by some, that the human fauna is to be succeeded by a higher one, as it has itself succeeded the lower. Should it be supposed that the ultimate submergence predicted is sufficiently remote to permit the interposition of a superior race of intelligences, I recall to mind the evidences that the lands are wasting and deteriorating; the river-beds are deepening, and diminishing the sources of irrigation; and all the populated regions of the earth are slowly approaching the desert condition of that ancient continent drained by the Colorado. Each continental surface in the geological succession is the exclusive gift to a single great fauna. A single race witnesses the disappearance of the freshness and fertility of the land. A new race would demand a thorough renovation, like that which immediately preceded the advent of man. Such a revolution the senescent forces are unable to inaugurate.

WE

CHAPTER XXXVII.

THE REIGN OF UNIVERSAL WINTER.

E open now another volume of geological records.
From this we glean another prophecy.

I have stated that the energies of the earth's internal fires are waning. There is a chain of effects which, when we trace them backward, conduct us to an ancient molten condition of the world. At a period comparatively recent, it was still so warm that tropical vegetation flourished within the arctic circle. At a remoter period, neither animal nor plant could endure the temperature which prevailed, nor the warfare which fire and water were waging with each other. We retain the solid monuments of a terrestrial condition which carries us still deeper into the heart of eternity; when the whole orb was a glowing ocean of incandescent lava, while yet the waters of the earth hung in invisible vapor upon the outskirts of the atmosphere, like a concealed foe meditating a secret attack upon a powerful enemy.

Few who have studied the physics of the globe, and fewer still who have deciphered geological records, doubt that such were once the temperature and conditions of our planet. From that state to this, it has passed by the simple process of cooling. We trace the footsteps of this progress at every stage, Through Azoic, Eozoic, Paleozoic, Mesozoic, and Cenozoic Ages, heat has been gradually wasted in space-the solid crust has been thickening-the surface conditions have been changing. The average temperature of to-day, instead of being a state that is destined

to perpetuity, is but a passing phase; and when we shall have passed away with the other transient existences around us, some succeeding intelligence, gifted with the power to travel from sphere to sphere, will note the world in an altered condition.

I step here upon ground which has been somewhat contested. It was long since alleged that if our world be still in process of refrigeration, a sensible reduction in temperature ought to have taken place in 2000 years. But no such reduction has been satisfactorily established, though it will be confessed that we scarcely have exact observations on temperature which are more than two hundred years old. It was also alleged that since a reduction of temperature must be accompanied by a reduction of volume, the rate of the earth's rotation upon its axis must have been accelerated. But Laplace has demonstrated from ancient observations on eclipses that the mean day has not been diminishedth of a second since the time of Hipparchus, or during an interval of 2500 years. These negative results have been opposed to the theory of Cordier in reference to the former high temperature of the earth, and it has, till recently, been customary to speak of the thermal, no less than the astronomical conditions of our planet as constant. Poisson, an eminent French mathematician, proved, as was supposed, that the heat escaping from the earth in the latitude of Paris was only sufficient to elevate the temperature of a column of water eighteen inches high the trifling amount of one degree and a half. Vogt, a celebrated German geologist, affirms that the existing temperature of the surface of the earth is but one twelfth of a degree higher than it would be if the earth were completely cooled to the core. According to the later researches of Pouillet, the heat communicated to the surface of the earth from the central fire is but one fortieth the amount received from