They naturally divide themselves into two great classes by their construction—(1) those that are earth-works; and (2) those that are constructed of stone.
In most cases the earth-works are so low and slight that they could not have been of much service unless crowned with palisades. They are usually on sites that are more susceptible of cultivation than the hill-tops which are the common positions of the stone-works, and hence they have suffered more generally from agricultural operations than the forts of stone. They are usually irregularly circular or oval in plan, consisting of a varying number of low embankments drawn round the summit of a natural eminence. The only one of which a scale-plan has been made is a very characteristic example (Fig. 250), on the Midhill Head, on the estate of Borthwick Hall, Midlothian.[98] The space enclosed by the embankments is 410 feet in length from east to west, and 284 feet in breadth from north to south. The embankments are four in number, occupying a space round the enclosure, varying from 130 feet to about 80 feet in breadth. They are nowhere more than from 4 to 5 feet in height. There are two entrances to the enclosed space at the ends of the oval, and a third on the south side. This example represents in a general way the class of earthworks of most frequent occurrence, consisting of a series of circumvallations enclosing the highest part of an eminence of no great elevation.
_Proc. Soc. Antiq. Scot._, vol. xiv. p. 254. The Society is indebted to the liberality of the proprietor, D. J. Macfie, Esq., for the plan of this characteristic earth-work, surveyed and described by Mr. W. Galloway, architect.
[Illustration: Fig. 250.—Ground plan of Earthwork on Midhill Head, Midlothian.]
The Hill-Forts which are constructed of stone sometimes consist of a single wall drawn round the brow of a hill, and enclosing the more or less level area which forms its summit. One of this description at Garrywhoine, in Caithness, is an oval enclosure about 200 paces long by 65 in breadth. The foundation of the wall is about 14 feet thick, and in some places 3 or 4 feet of its height remains. In the thickness of the wall on the east side the remains of two chambers are visible. There were two entrances to the area of the fort, one at the north end and the other at the south end of the hill. The entrance at the north end has three of the great corner-stones of the gateway still in position. They are single stones or flat boulders about 5 feet high, set on end, having their broad faces in line with the exterior and interior faces of the wall, and the ends in the line of the entrance which is 7 feet wide. Only one of the stones similarly placed remains at the south entrance. The dilapidation of this remarkable example of a stone cashel was due to the construction of a mill-dam in the valley below, the stones having been rolled down the hill to form the embankment. I notice it because it is the only Hill-Fort I have seen which still retains the stone-pillars of its gateway, and because the story of its demolition illustrates the fate of many of the most perfect and interesting remains of our country’s antiquity.