John MacCulloch

“ If the whole peninsula be viewed laterally, the conformity of the rocking stone to the mass on which it stands and to the other small stones which crown the summits, is such that the eye cannot detect it, so perfectly it seems in its place. ”

“ In time, the accumulated gravel is blown away by the winds, although in the deeper hollows it may often be found forming considerable accumulations.
The same solubility of granite in water, (to speak generally) is the cause of that wasting of the surface which these rocks undergo, and to which I have before attributed the enlargement of the vacuities at the surfaces of contact, and the separation of the prisms into detached masses. ”

“ On a smaller scale, a phenomenon of rare occurrence in Nature may also be suggested in aid of it. I mean the spherically disposed granite of Corsica, which exhibits the various constituents of granite formed round numerous centres, and producing those beautiful specimens still so rare in the cabinets of collectors. ”

“ That the wearing of these granites on the surface arises from the action of water, will be evident on examining the stones themselves, and the result of their disintegration. Wherever a stone is disintegrated by the most usual process, the oxidation of the iron which it contains, a change may always be observed to have taken place from the surface downwards to a more or less considerable depth in the stone. Sometimes even the whole mass of rock will appear to have undergone this gangrenous process at once, and to have become a bed of clay and gravel. ”

“ Similar granite balls have been seen in other places, so that their existence is well ascertained, and this is one of numerous instances, where the decomposition of a rock gives us most useful information with regard to its structure, and where without that aid, we should never have divined the secret of its formation. ”

“ The granite of this county is known to be in general split by fissures in different directions, but most commonly tending to the perpendicular and horizontal. By those it is divided into masses of a cubical and prismatic shape. Of the exceptions to this rule there is one among many other instances, in Shaugh rick near Plymouth. If we examine a rock of this kind near the surface of the soil, we shall find that the fissure is a mere mathematical plane, separating the two parts, and that the angles are sharp and perfect. ”

“ We can also easily conceive that in certain cases, the peculiar circumstances of which lie equally hid from us, the approximation of the spheres of crystallization may have caused the crystalline polarity of the several masses to interfere with each other, so as to have produced in many cases an irregularity still greater than this, and in some instances even entirely to have obliterated the appearance of central tendencies. ”

“ If the centre of gravity of the mass chances to be high and far removed from the perpendicular of its fulcrum, the stone falls from its elevation, and becomes constantly rounder by the continuance of decomposition, till it assumes one of the various spheroidal figures which the granite bowlders so often exhibit. ”

“ It is a matter of more difficulty to assign the cause of the change of figure which the masses undergo, by what process Nature "mutat quadrata rotundis."
Whatever disputes and doubts may have existed relating to the stratification of granite in general, I believe there is no one now who conceives the granite of Cornwall more than that of Arran or Mont Blanc to be stratified. ”

“ The summits of all these hills are covered with granite cairns in different states of ruin and disintegration, and their sides are strewed to great distances with the bowlders which have fallen from them at different times.
The migration of stones is here readily to be traced upon a scale easily comprehended. The granite of which these hills are composed is well known, and has been often described. ”

“ We need not be surprised that this regularity is not more constant, nor the forms more perfect, as we are unacquainted with the numerous circumstances which may determine the several centres of crystallization, or which may interfere with the ultimate regularity of the resulting masses. ”

“ It would doubtless be a great improvement on the statue of Saturn, to be furnished with a moveable head, but an inspection of the upper stone is sufficient to show that its centre of gravity is placed much too high to admit of the conditions requisite for the production of that effect. ”

“ Not only indeed have idle curiosity and ignorant speculation busied themselves in accounting for phenomena which many of the vulgar have deemed little less than miraculous, but learned antiquaries have tortured their inventions and have constructed religious systems for the purpose of explaining these very simple and intelligible natural appearances ”

“ It is certain that these balls, now rendered spherical by decomposition, have been quadrangular masses, and hence we may step, without any great hazard of unsound footing, to this general conclusion, that these masses of granite, which show marks of wearing on their surface with rapidities proportioned to their distance from a central point, have had their hardness, and probably their crystallization or formation, determined from that centre. ”

“ It is not necessary to call in the aid of long continued friction or distant transportation to account for the rounded form of these granite bowlders. The changes which they undergo in their places of rest, by their more rapid disintegration at the angles than at the sides, are sufficient to prove that this spheroidal shape may be produced by chemical action of air and water, without the necessity of any mechanical violence. ”

“ So inclined is the plane on which it rests, that it appears at first sight as if a slight alteration of its position would cause it to slide along the plane into the sea; standing as it does within two or three feet of the edge of the precipice. ”

“ A quantity of loose quartz gravel may be generally found near the points of contact, marking the progress of this disintegration.
In the trials which I have at different times made on it, the greatest force that three persons could apply to it was sufficient to make its outer edge describe an arc whose chord was 3/4 of an inch at 6 feet distance from the centre of motion. When suffered to return it vibrates for a few seconds before it falls again to rest. A force of a very few pounds is however sufficient to bring it into a state of vibration, and to maintain a visible motion. ”

“ An abstraction of its support, occasioned probably by the gradual disintegration and sliding of the summit of the hill, has permitted the lateral parts to fall away, leaving, in its present whimsical position, that part which happened to be best poised. It is unnecessary to suppose that the chisel of Druidism has been employed to reduce it to an image of Saturn. Natural causes are sufficient to account for its appearance. ”

“ If we turn our attention to granites which from their greater elevation above the present soil appear to have been longer exposed to air and weather, we shall find, as the first step to change, a gentle rounding of the angles, such as is exhibited in the drawing last cited, the Vixen Tor. ”