more than equals the height of Ben Nevis over the level of the sea. That coal-basin which extends along the flat richly cultivated plain which stretches from the south-eastern flanks of Arthur Seat to the Garleton Hills in Haddingtonshire, considerably exceeds three thousand feet in depth; and, could it be cleared out to the bottom of the Calciferous sandstones, and divested of the hundred and seventy beds of which it consists, as we have seen the deep hollow of the Compensation Pond divested of its water, it would form by far the profoundest valley in Scotland. Of the beds by which it is occupied, it is estimated that about thirty are coal, varying from several feet to but a few inches in thickness; and we now know, that though some of these coal-seams were formed of drifted plants and trees deposited in the sandy bottom of some great lake or inland sea, by much the greater number are underlaced by bands of an altered vegetable soil, thickly traversed by roots; and that, as in the case of many of our larger mosses, the plants which entered into their composition must have grown and decayed on the spot. And of course, when the plants were growing, the stratum in which they occur, though subsequently buried beneath plummet sound, or at least thousands of feet, must have formed a portion of the surface of the country either altogether subaërial, or, if existing as a swamp, overlaid by but a few inches of water. We have evidence of nearly the same kind in the ripple-markings which are so abundant throughout all the shales and sandstones of the Coal Measures from top to bottom, and which are never formed save where the water is shallow. Stratum after stratum in the whole ten thousand feet included in the system, where it is most largely developed, must have formed in succession the surface either of the dry land or of shallow lakes or seas; one bed must have sunk ere the bed immediately over it could have been deposited; and thus, throughout an extended series of ages, a process must have been taking place on the face of the

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globe somewhat analogous to that which takes place during a severe frost in those deeper lakes of the country that never freeze, and in which the surface stratum, in consequence of becoming heavier as it becomes colder than the nether strata, is for ever sinking, and thus making way for other strata, that cease to be the surface strata in turn. This sinking process, though persistent in the main, must have been of an intermittent and irregular kind. In some instances, forests seem to have grown on vast platforms, that retained their level unchanged for centuries, nay, thousands of years together in other cases the submergence seems to have been sudden, and to such a depth, that the sea rushed in and occupied wide areas where the land had previously been, and this to so considerable a depth, and for so extended a period, that the ridges of coral which formed, and the forests of Encrinites which grew, in these suddenly hollowed seas, composed thick beds of marine limestone, which we now find intercalated with coal-seams and lacustrine silts and shales. There seem, too, to have been occasional upward movements on a small scale. The same area which had been occupied first by a forest, and then by a lake or sea, came to be occupied by a forest again; and, though of course mere deposition might have silted up the lake or sea to the level of the water, it is not easy to conceive how, without positive upheaval for at least a few feet, such surfaces at the water-level should have become sufficiently consolidated for the production of gigantic Araucarians and Pines. But the sinking condition was the general one; platform after platform disappeared, as century after century rolled away, impressing upon them their character as they passed; and so the Coal Measures, where deepest and most extensive, consist, from bottom to top, of these buried platforms, ranged like the sheets of a work in the course of printing, that, after being stamped by the pressman, are then placed horizontally over one another in a pile. Another

remarkable circumstance, which seems a direct result of the same physical conditions of our planet as those ever-recurring subsidences, is the vast horizontal extent and persistency of these platforms. The Appalachian Coal formation in the United States has been traced by Professor Henry Rogers over an area considerably more extensive than that of all Great Britain; and yet there are some of its beds that seem continuous throughout. The great Pittsburg coal-seam of this field, a seam wonderfully uniform in its thickness, of from eight to twelve feet,-must have once covered a surface of ninety thousand square miles. And this characteristic of persistency, united to great extent, in the various platforms of the Coal Measures, and of ever-recurring subsidence and depression, which accumulated one surface platform over another for hundreds and thousands of feet, belong, I am compelled to hold, to a condition of things no longer witnessed on the face of the globe. The earth has still its morasses, its deltas, its dismal swamps; it has still, too, its sudden subsidences of surface, by which tracts of forest have been laid under water; but morasses and deltas cover only very limited tracts, and sudden subsidences are at once very exceptional and merely local occurrences. Subsidence during the Carboniferous ages, though interrupted by occasional periods of rest, and occasional paroxysms of upheaval, seems, on the contrary, to have been one of the fixed and calculable processes of nature; and, from apparently the same cause, persistent swamps, and accumulations of vegetable matter, that equalled continents in their extent, formed one of the common and ordinary features of the time.

My subject is one on which great diversity of opinion may and does prevail. But while entertaining a thorough respect for the judgment and the high scientific acquirements of geologists who hold that the earth existed at this early period in the same physical conditions as it does now, I must persist in believing that these conditions were in one important

respect essentially different; I must persist in believing that our planet was greatly more plastic and yielding than in these later times; and that the molten abyss from which all the Plutonic rocks were derived, that abyss to whose existence the earthquakes of the historic period and the recent volcanoes so significantly testify,-was enveloped by a crust comparatively thin. Like the thin ice of the earlier winter frosts, that yields under the too adventurous skater, it could not support great weights,―table-lands such as now exist, or mountain chains; and hence, apparently, the existence of vast swampy plains nearly level with the sea, and ever-recurring periods of subsidence, wherever a course of deposition had overloaded the surface. The yet further fact, that as we ascend into the middle and earlier Palæozoic periods, the traces of land become less and less frequent, until at length scarce a vestige of a terrestrial plant or animal occurs in entire formations, seems charged with a corroborative evidence. I shall not say that in these primeval periods

'A shoreless ocean tumbled round the globe,'

for the terrestrial plants of the Silurians show that land existed in even the earliest ages in which, so far as the geologist knows, vitality was associated with matter; but it would seem that only a few insulated parts of the earth's surface had got their heads above water at the time. The thin and partially-consolidated crust could not bear the load of great continents; nor were the 'mountains yet settled, nor the hills brought forth.' It would seem that not until the Carboniferous ages did there exist a period in which the slowly-ripening planet could exhibit any very considerable breadth of land; and even then it seems to have been a land consisting of immense flats, unvaried, mayhap, by a single hill, in which dreary swamps, inhabited by doleful creatures, spread out on every hand for hundreds and thousands of miles, and a gigantic and monstrous vegetation

formed, as I have shown, the only prominent features of the scenery. Burnett held that the earth, previous to the Flood, was one vast plain, without hill or valley, and that Paradise itself, like the blomen garten of a wealthy Dutch burgomaster, was curiously laid out upon a flat. We would all greatly prefer the Paradise of Milton

'A happy rural seat of various view;

Grooves whose rich trees wept odorous gums and balm;
Others whose fruits, burnish'd with golden rind,
Hung amiable, Hesperian fables true,

If true, here only, and of delicious taste:
Betwixt them lawns, or level downs, and flocks
Grazing the tender herb, were interposed,

Or palmy hillock; or the flowery lap

Of some irriguous valley spread her store,

Flowers of all hue, and without thorn the rose:
Another side, umbrageous grots and caves
Of cool recess, o'er which the mantling vine
Lays forth her purple grape, and gently creeps
Luxuriant; meanwhile murmuring waters fall
Down the slope hills, dispersed, or in a lake,
That to the fringed bank with myrtle crown'd
Her crystal mirror holds, unite their streams.'

Library.

Of California

It was during the times of the Coal Measures that Burnett would have found his idea of a perfect earth most nearly realized in at least general outline; but even he would scarce have deemed it a paradise. Its lands were lands in which, according to the Prophet, there could no man have dwelt, nor son of man passed through.' From some tall tree-top the eye would have wandered, without restingplace, over a wilderness of rank, unwholesome morass, dank with a sombre vegetation, that stretched on and away from the foreground to the distant horizon, and for hundreds and hundreds of leagues beyond; the woods themselves, tangled, and dank, and brown, would, according to the poet, have 'breathed a creeping horror o'er the frame;' the surface, even where most consolidated, would have exhibited its

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