The Loe Pool abounds with a peculiar trout, and other fresh-water fish. On its banks the Botanist may gather Corrigiola Littoralis.
In proceeding to the Lizard Point, which is about fourteen miles distant from Helston, we shall examine the line of coast south of the Loe bar. The interior of this peninsular region has an aspect of dreary and barren uniformity, and when viewed from the high granite ridge near Constantine, it appears like a table land elevated some hundred feet above the level of the sea, presenting hardly any indication of rupture or contortion throughout the whole extent of its outline. The view of the same region from the western shore of the Mount's Bay is still more striking and characteristic; the upper surface seems so exactly horizontal, that one might almost be led to conjecture, that every projecting ledge had been planed down until the promontory resembled a great artificial terrace.[128]
Near Gunwalloe Cove the geologist should notice the singularly contorted appearance of the slaty rock, which continues as far as a small cove north of Mullion, called Bolerium, where it runs under a Greenstone composed of Hornblende and Compact Felspar. The Greenstone prevails through the whole of this district, and appears to pass by a slow gradation into Serpentine, under which it lies, as may be distinctly seen near the south side of Mullion Cove.[129] A small quantity of Diallage is occasionally present in this rock, but the predominant ingredient is common Hornblende; and where this latter substance greatly predominates over the Felspar, it in some places assumes an earthy appearance and decomposes into a kind of Clay, which is used in the neighbourhood with excellent effect as a top dressing for grass lands.
Serpentine is the next formation which we discover in our progress, and is that which confers such singular interest upon this part of the county, since it occurs in no other part of England. This beautiful rock derives its name from the variegated colours and spots, supposed to resemble the speckles of a serpent's skin; it is principally of a dark green or brown, suffused with shades of red. It occupies not less than one-third of the area of the peninsula; the whole extent of Goonhilly downs rests on it. Its boundary is easily traced, says Mr. Sedgwick, by the brown scanty vegetation with which its surface is imperfectly covered; and the Professor might have added, by the growth of that beautiful heath, the Erica Vagans, for so congenial and essential would a Magnesian soil appear to its production, that notwithstanding its immense profusion on the downs, not a single specimen is to be found beyond the line which defines the boundary of the Serpentine formation, nor is it to be seen in any other part of England. Genista Anglica is also to be found on these downs.
About three miles south of Mullion, close to the shore, is the celebrated Steatite, or Soap Rock, which appears to run in veins[130] in the Serpentine, although Dr. Thomson is inclined to consider it as Serpentine itself in a state of decomposition. When it is first quarried it is soft, but by exposure to air it gradually hardens, although it never loses that peculiar soapy feel which characterises it. Dillwyn & Co. of Swansea have, at present, the works in their possession, by paying to the proprietor, Lord Falmouth, a certain annual sum. Its value in the manufacture of China depends upon its infusibility, and the property it possesses of retaining its colour in the heat of the furnace; the first quality is to be explained by the total absence of lime in its composition, the latter by the very small proportion of metallic matter contained in it. There is, moreover, another purpose which it serves, depending upon the peculiar property of Magnesian earth in preventing that degree of contraction[131] which always occurs in the fire when Alumina and Silica are alone made use of. Near this spot veins of Native Copper may be frequently seen at low water during spring tides, and a mass of this metal was once raised which weighed 104 pounds. Copper is the only metallic substance that has been found in any quantity in the Serpentine formation; and this has never occurred except native, as in the above instance, or in the state of Green Carbonate, so that the mining adventurer need not anticipate much advantage from it.
About a mile farther south is Kynance Cove, justly celebrated as one of the most interesting and extraordinary spots on the coast; the descent into it is extremely steep, and overhung with frowning crags; the cove itself is formed by a numerous assemblage of Serpentine rocks of a dark colour, and which exhibit a beautiful polish from the constant attrition of the waves at high water; in one part, these groups are so singularly disposed as to open a fine natural arch into a grotto, which penetrates deeply into the cliff; the largest of these pyramidal masses is termed the Asparagus Island, from its being the habitat of Asparagus Officinalis. One of the rocks in this cove exhibits a very curious phenomenon whimsically called the Devil's Bellows; there is a very deep chasm, through which the sea rushes like a water spout, preceded by a sub-marine rumbling, as loud as thunder; a flowing tide, accompanied with a swell of the waves, seems to be essential for the production of this effect. De Luc offers the following explanation of the phenomenon: "In the rock there is a succession of caverns, into which the agitated sea rushes by some sub-marine passage, and being dashed and broken against their sides, a large quantity of air[132] is thus disengaged from them, which becoming highly compressed, and not being able to escape beneath, in consequence of the perpetual entrance of the waves, is forced to pass with great violence and noise from cavern to cavern, until it forces itself, together with a column of water, through the opening above." Amongst these beautiful rocks may be seen Diallage of a brown colour; Jade; compact Felspar, or Saussurite; and Asbestus. Dykes of Felspar Porphyry are also to be observed in this spot. It is hardly necessary to inform the geological tourist that, in order to view this interesting scene to his satisfaction, he must contrive to arrive at a period near that of low water.
On the summit of the hill above this cove the Botanist will observe Geranium Sanguineum spreading itself in broad tufts. Campanula Rotundifolia also occurs here.