which they rested artificially formed, by cutting away a portion of the rock; but, on the other hand, natural causes can produce similar results. The stone itself, acting like an umbrella, protects the central portion of the bed, while weathering is going on all around it. Such stranded boulders, being generally large and fantastically placed on prominences, were pre-eminently calculated to awaken astonishment in the minds of the worshippers of the mysterious works of Nature. Hence the important position assigned to Rocking-stones in the Druidical system of worship invented by Stukely and other antiquaries of the eighteenth century.
The famous Rocking-stone at Pontypridd (Glamorgan), known as the Maen Chwyl, and weighing 9½ tons, was surrounded, about the year 1850, by a stone circle with serpentine avenues, in imitation of Dr. Stukely's Dracontia; and since then the Pontypridd megaliths have become the rendezvous of the adherents of the neo-Druidic cult of the serpent.
In the absence of historical records and scientific investigations it was formerly the fashion to regard all these primitive stone monuments as the work of the Druids, the so-called priests of the Celts. Against the theory that any of them were ever used as altars for human sacrifice, there is prima-facie evidence in the care taken to have the smoothest and flattest surface of the stones
