The line D being the only one which is vitrified, no marks of fire appearing any where else, is a striking and impor tant fact. This line extends from A to B on the sketch (Fig. 3), passing over the top of the hill, and in the only di rection in which a range of signals could be made, so as to be distinctly seen further up the country.
To be satisfied of the reason why the signal fires should be kindled on, or beside a heap of stones, we have only to imagine a gale of wind to have arisen when a fire was kindled on the bare ground. The fuel would be blown about and dispersed, to the great annoyance of those who attended. The plan for obviating the inconvenience thus occasioned, which would occur most naturally and readily, would be to raise a heap of stones, on either side of which the fuel might be placed to windward. To account for a large extent of vitrified matter, such as that along the line D, it is only necessary to allow the inhabitants of the coun try to have had a system of signals. A fire at one end, might denote something different from a fire at the other, or in any intermediate part. On some occasions, two or more fires might be necessary, and sometimes a fire along the whole line.
It is evident, that the people who formed the structure on Dun Creich, had no idea of applying fire for the pur pose of strengthening the ramparts, and had not even taken the hint afforded them by the effects of the signal fires. Hence we consider the appearances at this place as de monstrative of the fact, that the vitrifications have been oc casioned by the lighting of signal fires, to warn the inhabi tants of the approach of an enemy, or to convey the orders of a chieftain to his dependants. It appears too, that such signals have been common after the use of lime mortar was known, since we find on this hill the remains of a build ing constructed with it. This may have served the dou ble purpose of a watch tower, and the habitation of the people who had charge of the station. At the head of the valley are the remains of an old castle, with which the sta tion was probably connected. While on the top of Dun Creich, it occurred to us, that marks of fire would he found on a hill, which obstructed the view of Dun Creich from Strath Carron, a valley which branches from that of the Dornoch Firth. We went to the spot, and found several masses of melted stones. A few miles up Strath Carron, where a steep rock occupies an angle formed by the river Carron and a tributary stream, are the remains of a fort, built in the circular form of the Duns, (or Danish, or Pict ish forts, as they have been called,) with distinct traces of ditches and earthen ramparts in front. With this, also,
the signal station of Dun Creich may have been connected.
We believe that nothing similar to Dun Creich, or other vitrified forts, has been observed farther to the northward ; though it is probable something of the sort may exist at the head of other firths. The next we shall take notice of is the first we meet with to the southward, and is situated at the head of the Cromarty Firth. The name of the hill is Knock Farril, and it is one of those which arrested the attention of Mr Williams. It is about two miles from the town of Dingwall, in the county of Ross, and forms part of a double ridge, which bounds the valley of Strathpeffer on the south, and separates it from the valley of the river Co nan. The ascent from the east and west ends is compa ratively easy, but the sides of the hill are very steep. From the summit there is an extensive view of the Firth of Cromarty, and of the adjacent country ; and the hill of Craig Phadrick near Inverness, on which there are vitrifi cations which have been described by Mr Tytler, is dis tinctly seen. The flat area on the top is a good deal in clined towards the west ; its length being about 135 yards, and its medium breadth about 45. Round the area, and close to the edge of the hill, we find masses composed of stones cemented together by incited matter, irregular in their positions and size ; and extending at each end about 50 yards from the area. The vitrification is every where superficial, extending but a very little way among the stones. There is a considerable quantity of rubbish seen in the cuts which Mr Williams caused to be made across the area in different places. This rubbish appears to have been collected for the purpose of extending or forming the area on the top ; and it would seem that much labour had been bestowed in accomplishing in this manner what might, apparently, have been effected more easily by cutting down part of the summit. On the plan (Plate CCLX. Fig. 2), A, marks the cuts made by Mr Williams ; B what seems to be the vestiges of a hut, and C the remains of a well, or rather a tank for holding rain water ; for there is no appear ance of spring water issuing from any part of the hill. The area measures nearly an English acre. This station may have been chosen to give warning of the approach of ships up the Firth of Cranially, and was probably the signal-post of the castle of Dingwall, formerly the residence of the Earls of Ross.