The foundation of the whole is a stupendous group of Granite rocks, which rise in pyramidal clusters to a prodigious altitude, and overhang the sea. On one of those pyramids is situated the celebrated "Logan Stone," which is an immense block of Granite weighing above 60 tons. The surface in contact with the under rock is of very small extent, and the whole mass is so nicely balanced, that, notwithstanding its magnitude, the strength of a single man applied to its under edge is sufficient to change its centre of gravity, and though at first in a degree scarcely perceptible, yet the repetition of such impulses, at each return of the stone, produces at length a very sensible oscillation! As soon as the astonishment which this phenomenon excites has in some measure subsided, the stranger anxiously enquires how, and whence the stone originated—was it elevated by human means, or was it produced by the agency of natural causes?—Those who are in the habit of viewing mountain masses with geological eyes, will readily discover that the only chisel ever employed has been the tooth of time—the only artist engaged, the elements. Granite usually disintegrates into rhomboidal and tabular masses, which by the farther operation of air and moisture gradually lose their solid angles, and approach the spheroidal form. De Luc observed, in the Giant mountains of Silesia, spheroids of this description so piled upon each other as to resemble Dutch cheeses; and appearances, no less illustrative of the phenomenon, may be seen from the signal station to which we have just alluded. The fact of the upper part of the cliff being more exposed to atmospheric agency, than the parts beneath, will sufficiently explain why these rounded masses so frequently rest on blocks which still preserve the tabular form; and since such spheroidal blocks must obviously rest in that position in which their lesser axes are perpendicular to the horizon, it is equally evident that whenever an adequate force is applied they must vibrate on their point of support.

Although we are thus led to deny the Druidical origin of this stone, for which so many zealous antiquaries have contended, still we by no means intend to deny that the Druids employed it as an engine of superstition; it is indeed very probable that, having observed so uncommon a property, they dexterously contrived to make it answer the purposes of an ordeal, and by regarding it as the touchstone of truth, acquitted or condemned the accused by its motions. Mason poetically alludes to this supposed property in the following lines.

"Behold yon huge
And unknown sphere of living adamant,
Which, pois'd by magic, rests its central weight
On yonder pointed rock: firm as it seems,
Such is its strange, and virtuous property,
It moves obsequious to the gentlest touch
Of him, whose heart is pure, but to a traitor,
Tho' e'en a giant's prowess nerv'd his arm,
It stands as fix'd as Snowdon."

The rocks are covered with a species of Byssus long and rough to the touch, forming a kind of hoary beard; in many places they are deeply furrowed, carrying with them a singular air of antiquity, which combines with the whole of the romantic scenery to awaken in the minds of the poet and enthusiast the recollection of the Druidical ages. The Botanist will observe the common Thrift (Statice Armeria) imparting a glowing tinge to the scanty vegetation of the spot, and, by growing within the crevices of the rocks, affording a very picturesque contrast to their massive fabric. Here too the Daucus Maritimus, or wild carrot; Sedum Telephium, Saxifraga Stellaris, and Asplenium Marinum, may be found in abundance.

The Granite in this spot is extremely beautiful, on account of its porphyritic appearance; the crystals of felspar are numerous and distinct; in some places the rock is traversed by veins of red felspar, and of black tourmaline, or schorl, of which the crystalline forms of the prisms, on account of their close aggregation, are very indistinct. Here may also be observed a contemporaneous vein of schorl rock in the granite, nearly two feet wide, highly inclined and very short, and not having any distinct walls. On the western side of the Logan rock is a cavern, formed by the decomposition of a vein of granite, the felspar of which assumes a brilliant flesh-red, and lilac colour; and, where it is polished by the sea, exceeding even in beauty the Serpentine caverns at the Lizard.

Mr. Majendie observed in this spot numerous veins of fine grained granite, which he is inclined to consider as cotemporaneous; he also observed what, at first sight, appeared to be fragments, but which, upon closer examination, he pronounces to be cotemporaneous concretions; for large crystals of felspar may be seen shooting from the porphyritic granite into these apparent fragments. These phenomena are extremely interesting in a geological point of view, and well deserve the attention of the scientific tourist.

In Treryn cove, just below the site of the castle, Dr. Maton found several of the rarer species of shells, as Patella Pellucida, P. Fissura, Mytilus Modiolus, Trochus Conulus, Turbo Cimex, and T. Fascitatus (of Pennant.)

Before we quit this coast we beg to state, for the information of the geological tourist, that the Granite which we have just traced from beyond the Land's End to this spot, continues until within half a mile of the signal post near Lemorna cove, where it meets with a patch of slate, and is lost for about the space of three quarters of a mile. At the western extremity of this junction (Carn Silver) the mineralogist will find embedded Garnet-rock with veins of Epidote and Axinite. Here may also be seen the rare occurrence of a granite vein penetrating both the slate and the granitic rock.

But let us return.——About two miles north-east of the Logan rock, and in the high road to Penzance, stands the town of Saint Buryan, which though now only a group of wretched cottages was once a place of very considerable note, and the seat of a College of Augustine Canons; the latter was founded by Athelstan after his return from the conquest of the Scilly Islands, A.D. 930. The remains of the College were wantonly demolished by one Shrubshall, Governor of Pendennis Castle, during the usurpation of Cromwell.