hundred feet of millstone grit to be laid down on the top of the limestone.

This millstone grit is a new and a very remarkable element in our strange story. From Derby to Northumberland it forms vast and lofty moors, capping, as at Whernside and Penygent, the highest limestone hills with its hard, rough, barren, and unfossiliferous strata. Wherever it is found, it lies on the top of the "mountain," or carboniferous limestone. Almost everywhere, where coal is found in England, it lies on the millstone grit. I speak roughly, for fear of confusing my readers with details. The three deposits pass more or less, in many places, into each other: but always in the order of mountain limestone below, millstone grit on it, and coal on that again.

Now what does its presence prove? What but this? That after the great coral reefs

which spread over Somersetshire and South Wales, around the present estuary of the Severn, and those, once perhaps joined to them, which spread from Derby to Berwick, with a western branch through North-east Wales,—were laid down—after all this, I say, some change took place in the sea-bottom, and brought down on the reefs of coral sheets of sand, which killed the corals and buried them in grit. Does any reader wish for proof of this? Let him examine the "cherty," or flinty, beds which so often appear where the bottom of the millstone grit is passing into the top of the mountain limestone-the beds, to give an instance, which are now quarried on the top of the Halkin Mountain in Flintshire, for chert, which is sent to Staffordshire to be ground down for the manufacture of China. He will find layers in those beds, of several feet in thickness, as hard as flint,

but as porous as sponge. On examining their cavities he will find them to be simply hollow casts of innumerable joints of Crinoids, so exquisitely preserved, even to their most delicate markings, that it is plain they were never washed about upon a beach, but have grown where, or nearly where, they lie. What then, has happened to them? They have been killed by the sand. The soft parts of the animals have decayed, letting the 140,000 joints (more or less) belonging to each animal fall into a heap, and be imbedded in the growing sand-rock; and then, it may be long years after, water filtering through the porous sand has removed the lime of which the joints were made, and left their perfect casts behind.

So much for the millstone grits. How long the deposition of sand went on, how long after it that second deposition of sands took

place, which goes by the name of the

gannister," or lower coal measures, we cannot tell. But it is clear at least that parts of that ancient sea were filling up and becoming dry land. For coal, or fossilized vegetable matter, becomes more and more common as we ascend in the series of beds; till at last in the upper coal measures the enormous wealth of vegetation which grew, much of it, where it is now found, prove the existence of some such sheets of fertile and forestclad lowland as I described in my last paper.

Thousands of feet of rich coral reef; thousands of feet of barren sands; then thousands of feet of rich alluvial forest;-and all these sliding into each other, if not in one place, then in another, without violent break or change: this is the story which the lime in the mortar and the coal on the fire-between the tworeveal.

VI.

THE SLATES ON THE ROOF.

HE slates on the roof should be, when

THE

rightly understood, a pleasant subject for contemplation to the dweller in a town. I do not ask him to imitate the boy who, cliffbred from his youth, used to spend stolen hours on the house-top, with his back against a chimney stalk, transfiguring in his imagination the roof-slopes into mountain-sides, the slates into sheets of rock, the cats into lions, and the sparrows into eagles. I only wish that he should-at least after reading this paper-let the slates on the roof carry him back in fancy to the mountains whence they came; perhaps to pleasant trips to the lakes