The first monument we propose selecting for examination is Avebury, as the largest, and in some respects the most important of the class in this country. Stonehenge might at first sight seem to have equal claims to precedence, but it is exceptional. It is the only hewn stone monument we possess, the only one where trilithons are found with horizontal architraves, and where the outer circle also possesses these imposts. It is, in fact, the megalithic monument which exhibits the most civilized forms, and to prove its age and use would not necessarily prove those of any rude stone monument found elsewhere. Avebury, on the contrary, though larger than the others, is constructed on precisely the same principle. It has the enclosing vallum, with its ditch inside, like Arborlow, Marden, Arthur's round table, at Penrith, and others we shall meet with further on, while its circle and avenues are identical, as far as we can judge, with numerous examples found elsewhere. Before, however, proceeding to reason about Avebury, the first point is to ascertain what the group really consists of, which is a much more difficult task than would at first sight appear. Stukeley has introduced so many of his own fancies into his description of the place, and they have been so implicitly followed by all who have since written on the subject, that it is now no easy task to get back to the original form. [Illustration: 14. View of Avebury restored. _a._ Silbury Hill. _b._ Waden Hill.] The principal monument at Avebury consists of a vallum of earth nearly, but not quite, circular in form, with an average diameter of about 1200 feet. Close on the edge of its internal ditch stood a circle apparently originally consisting of about 100 stones, with a distance consequently of about 33 feet from centre to centre. Inside this were two other double circles, placed not in the axis of the great one, but on its north-eastern side. The more northern one was apparently 350 feet in diameter, the other 325 feet.[77] In the centre of the northern one stood what is here called a cove, apparently consisting of three upright stones supporting a cap-stone--a dolmen, in fact, such as we shall frequently meet with in the following pages. In the southern circle there was only one stone obelisk or menhir. These facts we gather from Stukeley and Colt Hoare, for all is now so completely ruined and destroyed, that without their description no one could now make even an approximate plan of the place. The stones that comprise these inner as well as the outer circle are all the native Sarsens, which occur everywhere on these downs. In some places, such as Clatford Bottom, about a mile from Avebury, they lie still in numbers sufficient to erect a dozen Aveburys, and many are still to be seen in the Bottoms to the southward, and indeed in every place where they have not been utilized by modern civilization. No mark of a chisel is to be seen on any of the stones now standing here.