At a vastly remote period a valley lay between Britain and Gaul—before ever they were Britain and Gaul—and through this well-wooded valley flowed a river. The coast-line of Britain then lay from one to two hundred miles to the west, where is now the great drop in the ocean depths from 100 fathoms to 300 or 400. Cornwall was a Mesopotamia, a land between two almost parallel rivers, one occupying the bottom of what is now the English Channel, the other being the Severn. At that time the Bristol Channel was another great valley. From Brown Willy to the Scilly Isles ran a lofty mountain range, towering into the sky, of which the present Bodmin moors, Carn Brea, Carn Marth, Tregonning Hill, etc., are but the abraded stumps. Not only were they much higher, but their present roots stood 300 ft. higher than at present.

Then ensued a sinking of the land, and the Atlantic flowed into the valley to the south and joined the North Sea; and at the same time the Bristol Channel was formed. Thus the present coast was approximately outlined.

At some period shortly after, a vast inundation swept over the land from the north, and carried down the degraded granite, depositing the tin beds in the hollows. As early as 1830, Mr Carne noted: "The peculiar situation in which nearly all the stream tin of Cornwall is found is highly illustrative of the direction in which the current of the deluge swept over the surface. All the productive streams are in the valleys which open to the sea on the southern side of the Cornish peninsula; whilst most of the richest veins are situated near the northern coast."

The deposit of tin stone, or tin ground, lies directly on the shelf, or primitive surface of rock, and is carried far out in the estuaries, and overlaid by marine deposits.

In 1828, in Carnon Creek, a cairn was discovered 16 to 18 ft. below the surface, and that surface 4 to 5 ft. below low water mark. In it was a crouched skeleton. This shows that there must have been a subsidence of the land of something like 30 ft. at least since the period when man in the late stone or early bronze age inhabited Cornwall.

The submarine forests grew on the top of the tin ground. Of these many have been noted and recorded, not only on the south coast, but on the north as well. The trees were oak and hazel, alder and elm, but they never reached a large size.

Above this bed lie the raised beaches, some 40 or 50 ft. above high water mark. The tin-beds in the Cornish valleys towards the sea do not exhibit such an upheaval. Generally the raised beach rests on the original rock, and consists of rolled stones, frequently of large size, mixed with smaller gravel and sand. The "Head of Rubble," with some intervening perplexing beds of sand, may be noticed on the coast. This Head is from 40 to 50 ft. in depth. It is composed of angular fragments of rock, often large, many of quartz, with no signs of stratification. The Rubble bed in Cornwall has yielded no organic remains, but elsewhere in it have been found the bones of the mammoth, elephant, woolly rhinoceros, reindeer, etc. It was not formed by the disintegration of the subjacent rocks, but by aqueous transport. It owes its origin to a powerful force of water, acting violently and rapidly. It caps the heights, and is not in the valleys where the tin ground has been deposited. It has not therefore been found to overlie it. It was due to a sudden and brief overrush of water, and the fragments of stone carried before the flood did not travel sufficiently far to have their angles rubbed down.

Perranporth Rocks

Perranporth Rocks

As may well be supposed, the action of the sea on the coast-line has been affected largely by the character of the rocks against which the waves have lashed themselves to foam. Where the rocks are of granite or slate, the tide and the waves have very little effect upon the outline of the coast; it is in those places where the softer rocks prevail, and where exposure to the prevalent wind induces breakers of great volume, that the loss of land by the action of the sea is greatest. In fact, the tides rarely run beyond one or two miles per hour, except round headlands, and it is where the rocks are of a yielding character that the coves and bays are formed. This is not always the case. Where the sea has found a fault in the rock it will burrow incessantly till it has bored out for itself a cavern, and the head of this falling in produces a tiny cove. The hard quartzose and trap rocks of Trevose Head, the greenstone rocks of Pentire, near Padstow, the hard slates of St Agnes, the greenstone and hardened schist of the Gurnard's Head, and the granite of the Land's End, defy the action of wave and tide. But it is otherwise where, for instance, the Head of Rubble occurs. "In Gerrans Bay it is plain that the cliffs of Head were at one time much further out than they are now. The tops of the earthy cliffs are split with cracks and miniature chasms, showing that great masses are constantly being detached by atmospheric causes, while the great heaps of earth at the foot of the cliffs show how for centuries masses of earth have rolled down from their tops on to the beach below[1]." As to the kingdom of Lyonesse, which was supposed to extend from the Land's End to beyond Scilly, it never existed in the historic or prehistoric period. Another fable that may be dismissed, is that St Michael's Mount was surrounded by a vast tract of woodland, in which were villages, and where settled hermits. It did rise above a forest, but that was in a prehistoric period. But if the sea gains on the land but imperceptibly in one way, it gains in another on the north coast, by the action of the wind carrying the sand inland, and overwhelming field after field. It is not a little curious to mark, nevertheless, how a small dribble of a stream will arrest the onward march of the sand-dunes.

At Constantine by Padstow as already said the old church is enveloped in sand-hills, so is that of St Enodoc. The Perran Sands have so encroached that they extend over a mile and a half inland and have in process of time swallowed up two churches and a village. The Gear Sands have even climbed a hill to the height of 300 ft. The Godrevy, Upton and Phillack towans have moved inland from St Ives' Bay and engulfed the residence of the ancient kings of Cornwall at Riviere.

The same phenomenon has not taken place in the south, but there the estuaries have been silted up by the wash from the stream tin works. Formerly boats could come up to Tregony. Now the Fal is choked with detritus for miles down. Restronguet creek bore vessels to Perranarworthal. Now it is completely silted up, only a trickle of water running down through desolate morasses and flats resulting from the workings of the miners.