Continuing our route towards Cape Lizard, we shall perceive that the Serpentine terminates about half a mile before we reach it, and is succeeded by Micaceous Slate, under which, at the Lizard head lie alternate beds of Compact Felspar, containing specks of Hornblende and green Talc. There are two light-houses at this point which front the south, and stand nearly abreast of each other, but unhappily they are too often found to be insufficient securities against the darkness of the midnight storm, and the treachery of the sunken rocks with which this stern coast is beset. Foreign pilots, unacquainted with its perils, seldom keep the necessary distance from the shore, and from the steepness of the rocks no kind of assistance can be afforded to the mariner from the land.

On a low hedge under the light-houses is to be found Herniaria Glabra. It was here in the pursuit of this very plant that a well known Botanist, during the late war, was seized as a spy by the suspicious natives, and carried to Helston for examination. The increased intercourse, however, with scientific travellers, will render the recurrence of such an event impossible.

The name of the promontory was most probably derived from the striking contour which it exhibits when viewed from sea, resembling the elongated and compressed form of the Lizard; at the same time it must be observed, that the colour of its rocks resemble also that of the animal to which we allude, while the British words Lis-ard signify a lofty projection; these are extraordinary coincidences, and are well calculated to fan the flame of etymological controversy.

If after visiting this promontory, the traveller feels inclined to trace the different rock formations, and to complete his geological survey of the Lizard Chersonesus, we recommend him to return by a circuitous route along its eastern coast. Greenstone reappears about half a mile east of the Lizard Point, and continues for some distance, with the occasional interruption of Serpentine, which dips towards the sea. This latter rock will be found best adapted for œconomical purposes at the Balk Hill, Landewednock, but it is certainly far inferior to that worked for chimney pieces, columns, &c. from the quarries in the Isle of Anglesea. Near Cadgwith the rocks on the coast form a very interesting and extraordinary amphitheatre, which is termed by the inhabitants the Frying Pan, although the appellation of Cauldron, which it strongly resembles, would be much more appropriate. Its sides are nearly two hundred feet in height, and, at high water, the sea enters it and boils up through an arch near its bottom. In this spot the position of the Serpentine upon Greenstone is very apparent. Beyond Cadgwith the Serpentine assumes a dark green colour, and contains small masses of the emerald green Diallage, or Schiller-spar; whence it continues to constitute the coast round the Black Head to Coverack Cove. About a mile from the coast at Gwenter, the rock denominated by Abbe Haüy "Diallage Rock" (Gabbro) presents itself to our notice; it is composed of Saussurite, or Compact Felspar, and Diallage Metalloïde. In a quarry near this spot it may be seen to join Serpentine. In the Diallage Rock, at a small village near the coast called Gwendra, as well as in the rock of Saint Keverne, Mr. Majendie discovered some small metallic specks, which he found on chemical examination to consist of Iron, with a portion of Titanium. Some of the same substance was immediately transmitted to Mr. William Gregor, who stated that the results of his experiments proved it to be an assemblage of several ingredients, viz. Silica, Alumina, and the Oxides of Iron and Titanium, with a little Potass. Some of which ingredients were no doubt derived from the gangue with which the metallic substance is intimately mixed. This is a discovery no less curious than important, and would seem to point out the origin of the Menachanite, in which Titanium was first discovered by Mr. Gregor.

The great mass of Serpentine ends at Coverack Cove, a spot which well deserves the attention of the Geologist, as offering a series of rocks of a very mixed character; these consist of green and reddish-brown Serpentine, with the Jade of Saussure, (the feldspath tenace of Haüy) and Diallage[133] of the green and metalloïde varieties; some of the Felspar found here is of a violet colour, and is striated like that of Labrador. In beds which lie below high-water mark in this Cove the mineralogist may obtain masses of Diallage Metalloïde, six or eight inches in length.[134] A beautiful rock succeeds and continues for three miles along the coast to the Manacles; and in the interior of the country it predominates through the greater part of the parish of Saint Keverne. It has compact Felspar for its base, in which are imbedded crystals both of Diallage and Hornblende. In the proportion, as well as the magnitude of these constituents, says Mr. Professor Sedgwick, there is such an unusual variety, that we were almost led to conjecture, that during the deposition of the mass many conflicting principles had been in action, not one of which was long able to keep the mastery over the others; there are for instance many large blocks which in one part resemble a fine Greenstone, and in another, a coarse porphyritic Diallage Rock; within the distance of a few feet these varieties may be observed to alternate repeatedly, sometimes in the form of stripes, but more frequently in amorphous concretions separated from each other by lines which are perfectly defined. Schistose Greenstone occurs again at Porthowstock, and a small bed of Serpentine, on the south-west side of Porthallo in the cliff, which rests on a reddish Talc which lies, as before, on Clay-slate. No other variety is observable from hence to the Helford River, except in the appearance of a Pudding Stone, or Conglomerate, near the Dennis Creek, composed of rounded fragments of Slate in which veins of Quartz are distinctly visible. The traveller will not fail to visit the stream of Tregonwell Mill,[135] near the village of Menacchan, celebrated as the habitat of the Titaniferous Iron (Menacchanite, or Gregorite) discovered by the late celebrated Mr. William Gregor.[136] He will also receive much gratification by extending his route to Mawnan Cliffs, where he will observe a most extraordinary intermixture of fine and coarse grained (Grawacke?) slate, which are traversed by many contemporaneous veins, some composed of Quartz, and others of Ferriferous Carbonate of Lime; some small cavities are coated with fine spicular Arragonite, and a much rarer substance, which on a chemical examination by Mr. Gregor proved to be a Sub-carburet of Iron, has been found in thin plates among the laminæ of the Slate. The Reverend John Rogers has also obtained from this spot small octohedral crystals of the Yellow Sulphuret of Copper.

From a general review of the phenomena developed in the present excursion, Mr. Professor Sedgwick is led to conclude, that the great Plateau of the Lizard is not composed of stratified rocks, for although some obscure indications of an order of super-position appear near Coverack and Porthalla, yet he considers them as being too uncertain to be opposed to the clear evidence offered to the south-eastern parts of the coast, where the alternating masses of Greenstone and Serpentine so often appear, like great wedges driven side by side into the escarpment, without any arrangement whatsoever. Mr. Majendie, however, who, be it known, actually bivouacked in this district for a week, was satisfied that the Greenstone and Serpentine did exhibit characters of Stratification.—But we desist—feeling what no doubt our readers have likewise experienced the dry and uninviting nature of Geological details.—Having therefore completed the task we assigned ourselves, and conducted the traveller to the more prominent and interesting objects of Western Cornwall, we take our leave. The Agriculturist, the Antiquary, the Botanist, the Geologist, and Mineralogist, must, each in his turn, have received ample gratification and instruction from his visit to this interesting and important district of the British Empire, while the Capitalist must have seen from the agriculture, the mineral treasures, the fisheries, and the commerce of the country, how many, and what great opportunities are presented for the advantageous exercise of capital; the Valetudinarian too has, as we sincerely hope, derived his share of benefit from the excursions, and felt the salutary influence of those mild and genial breezes which clothe our fields with perpetual verdure, and impart to our cottagers the enviable blessing of Health and Long Life.

FOOTNOTES:

[123] Before his departure upon this excursion, we recommend him to examine the very instructive suite of specimens which were collected, and deposited in the Cabinet at Penzance by Mr. Ashhurst Majendie, a gentleman whose geological labours in this country are well known, and whose zeal and ability so greatly promoted the early advancement of our Geological Society. This valuable series has been greatly augmented by a Collection since presented to the Society by The Reverend John Rogers. The Geological tourist ought at the same time to make himself acquainted with the observations of Mr. Majendie "On the Lizard District," in the first volume of the Transactions of the Royal Geological Society of Cornwall; and those of Mr. Professor Sedgwick, on the same subject, in the Transactions of the Cambridge Philosophical Society.

[124] In the Greeb-rock, an insulated mass of greenstone in the sea beneath, there is a vein of Asbestus-Actynolite, mixed with Axinite, from four to twelve inches wide. This is a curious spot, well worthy the attention of the geologist.

[125] As will appear on the perusal of the first edition of this little work.