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There rolls the deep where grew the tree.
0, earth! what changes hast thou seen!
There, where the long street roars hath been
OTWITHSTANDING the absence of lofty sea-worn cliffs,
of mines, quarries, and other sections of the ground within
a walking distance of Town, the Londoner who wants to spend a Saturday afternoon at field-geology is not without suitable resorts. The insight we obtained last Saturday into the history of that upper formation of our Middlesex landscapes, that range of soft and argillaceous earth, the London Clay, as we strolled in those well-worn haunts near Hornsey Wood
Nourishing a youth sublime
—this insight, we say, teaches us Londoners how much nearer home than is commonly supposed are some of the most wonderful and typical illustrations of geological change which our earth affords. In these days of eager touring to distant shores in search of new sensations, it is not an unwholesome lesson to learn that
For things far off we toil, whilst many a good
In our Hornsey ramble we saw how even that unpromising subject for mental entertainment, the much-abused clay of our London environs, is not without a romantic history. How seldom, as we have walked on its dull and pasty surface in the falling rain, or avoided its gaping fissures in the drought of summer, marking the contours of its grass-clad hills, have we remembered that we were straying amid the reefs and shoals of an ancient sea-bed! How little did we think that this sea-bed, which now forms most of the surface soil of this county of Middlesex, is the tomb of countless generations of marine creatures; that it is the grave of gigantic sharks and crocodiles, as well as of the most minute and beautiful of shell-fish-a fauna of a kind which indicate an almost subtropical temperature existing in these latitudes at a pre-historic period of the earth!
Thus we moralise--we, a small company of the Saturday Halfholiday persuasion—as we emerge from the purlieus of Cheapside, and start together on our second journey of exploration in our London environs. The enfranchised of the Saturday Half-holiday —merchants, warehousemen, clerks, shopmen, ard British workmen with flag-baskets-are setting in a steady current to the “Underground" to make their exodus from the stale and dingy City to green lanes, meadows, and country roads. We drift into the stream and are soon en route for Highgate, viâ the Great Northern and Edgware and Highgate Railway.
Our equipment as field-geologists is of the modest and rudimentary order. It consists of a hammer for fracturing flints and septaria, a Coddington lens, a pocket compass, and a miniature map of the environs of London, with the elevations conspicuously shown. Our principal object this afternoon is to study the surface configuration of the district we visit. Physical geography, in fact, rather than mineralogy, is the aspect which geology will bear towards us to-day. This is a pursuit in which the most uninitiated may join us. It requires no antecedent technical knowledge, nor does it involve that continuous stooping down for microscopic researches which so often renders a naturalist's excursion a weariness to the flesh. With our eyes free to range round the horizon, we proceed on our way to Hampstead Heath.
When on the country road, let the Saturday afternoon rambler who would get a little cheap geological recreation never fail to note any strange stones that come in his way. Here, for instance, in Hornsey Lane, are samples of Rochester flints, brown-stained and water-worn ; Mount Sorrel granite, and trap-rock (the latter a blue stone which we have seen quarried from the mighty cliff of Penmaen Mawr during our summer holiday), all of which are used for road-mending. Again, never let us lose an opportunity of sound
ing the British navvy upon questions of which he is almost necessarily a special authority. Approached properly, he is found to be an excellent referee for the local information you want information which is seldom to be got from books. Here are half-a-dozen of the brotherhood, busy upon a new sewer.
In a few minutes we are on conversing terms with one of the party. This man has worked for many years in the soil of North London, and is familiar with all its varieties. He has learnt where are the best fossil grounds, and where, on the other hand, the fossils are missing for miles together. He has found "shells" plentifully at the diggings for the new hospital at Highgate, at the excavations for Gatti's ice-house in Copenhagen Fields (quite an historical spot for fossils this), and at Finsbury Park. At Finsbury Park, last summer, during the excavations for the new reservoir, sharks' teeth, he tells us, were found in abundance.
Here, in Hornsey Lane, just thrown up from the excavations by these navvies, is a white and glassy.looking object, glittering in the clod of dull-coloured earth, and looking quite foreign to the soil. On taking it up we find it to be the mineral selenite. Our navvy prefers to call it “congealed water." His
' account of it is in remarkable coincidence with the fact that the substance itself is actually named from the Greek word signifying the moon, owing perhaps to a common belief that the crystals of selenite are really water congealed by the influence of the moon.
Chemically, we are told selenite is found to be a sulphate of lime. Is is a transparent variety of gypsum, a material in which the Paris basin abounds, and which is calcined into plaster of Paris. It is worth remembering that the massive variety of gypsum called alabaster is sometimes found as transparent as the crystal we now hold in our hand, and is used in some countries of South America as window-glass. We will pocket our specimen of selenite, and label it at leisure with its name and locality.
Here is Highgate Archway. Over the balustrade on the London side, and down in the cutting at the foot of the fir trees, the bright Bagshot Sand gleams out upon us. We are now getting above the horizon of the London Clay, which is here about 480 feet thick. We push on for the Gatehouse Tavern, and then turn into Hamp
stead Lane for the Heath. The silver birches of Caen Wood and two remarkable hornbeam hedges yield us a note for a botanical excursion; the Bagshot Sands again appear to us in section (this time in a field to our left), and now we are at “The Spaniards.”
The expanse before us, then, is Hampstead Heath ! This is the spot which nature and tradition have endeared beyond all other heaths and commons to the jealous Londoner! Where are tho beauties and charms of the place ? Where is the blossoming furze that gladdened many a sunny bank, in which bees and butterflies delighted, that so gladdened the great Swedish naturalist ?
Surely the floral beauty of Hampstead Heath must be all of the past, and its memory all that remains. It lies before
abused and ravaged as if of malicious wickedness. It everywhere exhibits great gaping unstaunched wounds. Whole acres have been mercilessly flayed of the beautiful heathery covering, and made to show a hundred hideous sores. Two or three melancholy oaks, perched up in strange isolation, appeal to the eye of the visitor, and tell the tale of their wrongs. Their roots are all bared and exposed, and they look like the Screw-Pine of the tropics, instead of a familiar British tree. They tell of the spoiler's visit with the sand-cart, and add to the dreariness of the scene.*
Still there are relics of scenery at Hampstead Heath which recall the pictures of Constable. Such precious bits may be found as we enter the Heath from “The Spaniards,” and leave the road at once for the greensward on the right. Here the ground is well broken, and is still clad with some of the old vegetation. In the hollows, where furze bushes, heather, and blue-bells still linger, and where the horizon is rich in contours and distances, we find in the autumn swarms of artists, with campstool and easel, seeking to recover the traditions of the landscape.
Elsewhere, we have made the fol.
lowing note upon Geological Scenery at Hampstead :—Hampstead Heath is a good and obvious example of the way in which the natural scenery of a locality is determined by its geological structure. Here at Hampstead is a patch of wild heath, reminding us of Surrey. At Hampstead, contrasting with the rich pastures, oaks and elms of Middlesex, are the fir-trees, gorse-bushes, and sandy wastes of a Surrey heath. The difference is simply geological in its origin. The heath-scenery at Hampstead is solely the product of the underlying sands, as the prevailing scenery at Middlesex is the product of the clay. Hampstead Heath is, in fact, a detached and outlying portion of the main formation which lies in Surrey and other southern counties. Highgate and Harrow are its only companion outliers in Middlesex. This geological character of Hampstead explains why the Heath has remained unenclosed and common land. The ground is a flinty sand, and does not form soil. Being
But let us push on to Hampstead Hill, and gain the highest ground. It is on Hampstead 'Hill that we can best get an insight of the geographical history of the Thames Valley. Hampstead Hill is the summit of the northern London slope of this valley. On the top of the opposite slope is Norwood Hill, the summit of which is about eighty feet lower than Hampstead Hill. The valley between Hampstead Hill and Norwood Hill is about eleven miles across.
What has been the history and origin of this valley? Has it always existed ? If not, have we any data for discovering the pre-existing configuration of the country? Have we any evidence as to how this valley, as it here begins to be the estuary of the Thames, was formed ?
Here is the answer of the geologist to these questions ; let us give it the severest scrutiny :
The Hampstead and Norwood Hills are but isolated portions of a great mass of stratified clay which at one time occupied the intervening lower space in which London now stands. *
We will first amplify and illustrate this startling statement. It has been said that we are separated from the Norwood hills by a valley of a width of about eleven miles. Now there was a time when a line drawn from the spot we now call Hampstead to a point of eighty feet above the present Norwood Hill would have marked a continuous horizontal level of clay stretching from its one point in Middlesex to the other in Surrey. The intervening valley, over which we now cast our eyes, has been excavated in the course of ages from the vast, solid mass which once filled the space.
What is the evidence for this bold statement ? The evidence is stratigraphical, as geologists say, and it is also biological. The
unsuitable for agriculture, it has remained open and unappropriated from time immemorial. The sand at Hampstead probably varies from 60 to 80 feet in thickness. (W. Whitaker, Geological Survey, 1864). Hampstead Heath, both as a product of Nature and as common land, is the gift of the Bagshot sand.
· Prestwich, The Ground Beneath Us...