stratigraphical evidence will be best comprehended in the light of such a passage as this on "Valley Formation." It is from a writer of the last century, named Catcot, the author of a treatise on the Deluge. He says,

"If a person were to see the broken walls of a palace or castle that had been in part demolished, he would trace the lines in which the walls had been carried, and in thought fill up the breaches and unite the whole. In the same manner, when we view the naked ends or broken edges of strata on one side of a valley, and compare them with their corresponding edges on the other, we cannot but perceive that the intermediate space was once filled up and the strata continued from hill to hill."

Now this theory evidently requires that the strata at Hampstead and Norwood should be horizontal. Let us test it by walking to the nearest sand-pits, and viewing the sections which are there revealed. If this Hampstead-hill had been upheaved by local forces operating just below it, we should see the strata in convex curves. But the strata, as we may see, are horizontal. To complete our case, Norwood-hill, although it has lost its corresponding capping of Bagshot Sand, and therefore does not rise so high as Hampstead-hill, is known to consist of strata lying in the same horizontal lines. The numerous sections which have been made in the London Clay for wells, sewers, and railways, have revealed the existence of the same lines of strata, on each side of the valley, lying in the same horizon, and under circumstances which show them to have been once connected.

Here is a list of some of the wells which have been sunk through the clay between Hampstead and Norwood, and which have supplied evidence of the previous continuation of the strata at a height of nearly 500 feet above the present high-water mark. It will be observed that the depth of the clay, as is required by the theory, decreases as we leave the brow of the valley on either side and approach the scene of the deeper excavation.

The organic remains of the London clay at Hampstead and Norwood confirm that continuity of the strata which has been asserted, and form the biological evidence of which mention has been made. These organic remains have been found in distinct zones of depth, each of which is characterised by a particular species of fossil, or by a large development of a few particular species. The horizon of these zones is the same on either side of the valley, and testifies to their former connection.

Here, then, if we Londoners care to see near our own home some example of enormous geological change, is one of the most typical and impressive memoirs of landscape history. We find that the elevations which, to us in these modern times, are the hills of Hampstead and Norwood, were not hills in the original configuration of the country. They became so, in the course of remote and incalculable years, by the degradation and waste of the formation of clay and sand, the original level of which these familiar hills of our suburbs are left to indicate. Of this formation of clay, which once extended uniform in its depth through the London Basin, and which still stretches horizontally from Newbury to Harwich west and east, and from Hertford to Croydon north and east, how little now remains! Here, at Hampstead Heath, we see one of the original levels, for here the next overlying formation, the Bagshot Sand, begins. Here the depth of the London Clay is about 480 feet. Yonder Thames Valley shows a depth of nearly 500 feet from which the strata are missing. Between us and the opposite hills eleven miles of excavation have also to be reckoned at this section alone of the valley. When we are informed that all that now remains of the London Clay throughout the entire basin is a mean depth of about 200 feet, we gain some impression of the lapse of time required for the wear and transport of the missing earth of the valley before us, and of the volume of the waters

by which in remote geologic ages the Thames Valley was excavated.*

Looking, then, at these stupendous operations of Nature which lie under our own common observation in the suburbs of London, what insight do we gain into the economy and history of the earth's surface! Of how many elevations, which, like those we have been studying at Hampstead, were monuments of a past world-surface now broken up and destroyed, might it have been said

The hills are shadows, and they flee

From form to form and nothing stands;

They melt like mist the solid lands,

Like clouds they shape themselves and go.

These discoveries and these reflections, together with a bag of minerals and specimens of coloured sands we have collected, well reward us for our Saturday afternoon at Hampstead Heath.

*In looking from Hampstead (or any other eminence that affords a view of the Thames near London,) for the V-shape of the typical valley, it is to be remembered that the Southern slope of the Thames Valley has been broken up by subterranean convulsions (that took place when the land-surface of this part of England was acquiring its present drainagesystem and landscape-contours), so that

but little approach to the V-shaped excavation which the word valley conveys is now to be discovered on the Southern side of the Thames. But the hills that are left-Shooter's Hill more obviously than Norwoodstand up out of the ruins to tell of the once continuous summit-line of the valley-slope on the Kent and Surrey side of the river.

No. III.

LONDON PARK AND FOREST TREES.

For June is full of invitations sweet.

'Tis good to lie beneath a tree,

While the blithe season comforts every sense,

Steeps all the brain in rest,

Brimming it o'er with sweetness unawares.

Under the Willows.-J. R. LOWELL.

UR suburban explorations on the Saturday afternoon have hitherto engaged us on the underside phenomena and mysteries of the ground beneath us.

We have begun an acquaintance, to be continued hereafter, with the underlying worlds of fossil creatures-organic forms of beauty, of terror, or of wonder; and have had some glimpses far back into the "speechless past" of our venerable earth's long history. But how different the aspect, and how opposite the charm which never-resting Nature—

Great Nature! ever young yet full of eld!

has provided since the first afternoon of our rambles! It was the month of the still lingering winter, when from beneath the ribs of death the earth began feebly to send up her tentacles in search of the sunlight. How transfigured now is the landscape, with its blossoming hedge-rows, its leafy woodlands, its ample vesture of verdant grass, which everywhere conceals and adorns the aged world! This Spring-time of floral birth is daily dedicating new beauties to the sun, and inspiring once more the grateful strain—

THOU renewest the face of the earth!

To some of us Londoners, who have been used in earlier years to "walk the woodland aisles among," it is one of the freshest delights of the returning Spring to renew our acquaintance with our forest trees. True, there are other resources than those of tranquil Nature to beguile our Saturday Half-holiday hours. But how many among us are unequal to the muscular sports to which,

for the most part, the newer generation of men in London devote their Saturday's leisure? The less robust and the sedentary give themselves in a quiet way to such rural rambles as ours. At the end of the week they want rest and solace for the brain. They feel, with the author of Under the Willows, that—

The brain,

That forages all climes to line its cells,
Will not distil the juices it has sucked
To the sweet substance of pellucid thought,
Except for him who hath the secret learned

To mix his blood with sunshine, and to take
The winds into his pulses.

But their out-door pleasures are of a soothing and restful kind.

Let us away, then, this Saturday of early June, from the stony rattle of the City to some tranquil purlieu of Nature. Without aspiring to be botanical, or perplexing ourselves with technical names, let us take up the rights which vest in us as unlearned and ordinary mortals, and claim our inheritance in the trees of the landscape. For how many of us have yet done this with intelligence and insight? How long shall it be to the discredit of modern English society that so few of us are able to distinguish, as we walk the rural highway or the woodland, the half-dozen species of our commoner park and forest trees; to read in the physiognomy or the leaf of the individual, the tribe to which it belongs? There are many, doubtless, who can tell an oak from a hornbeam (especially if they see the acorn); many, again, can easily distinguish the horse chestnut (particularly when it is in blossom). But what of the poplars (other than the spiral Lombardy, which is not the commonest form)? What of the sycamore, maple, and plane, the willows, the alders, the birches, and the elms? What of our glorious pines, in these northern latitudes the "princes of vegetable nature," as Linnæus has said of the palm-trees of the tropics? Of our evergreen grandiflora, as well as of our deciduous trees, what charms still remain to tempt or to shame us into study, admiration, and delight! Then whilst the foliage in park and forest is still umbrageous and vivid, let us give an afternoon to atone for the neglect of the past! Let us enter some leafy cathedral through whose lofty clerestory the sun shall glint athwart with