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.