An interesting feature connected with the glaciation of Caithness is the development of moraines and morainic deposits in several parts of the county. Hitherto they have not been described. In Strathmore they are well developed, and they stretch far down the valley to the edge of the great plain. The most easterly limit of the moraines and gravels is at Dalemore, about a mile to the East of Dirlot Castle. This point is situated about fourteen miles from the county boundary at the head of the strath. Near Westerdale, about a mile to the north of Dirlot, the grey shelly boulder clay forms a great plain, through which the Thurso river has cut a channel, and formed an alluvial terrace. This platform of boulder clay is dotted over with conical heaps and ridges of sand and gravel, at a height of 200 feet above the sea. Sections of these heaps are exposed by the roadside on the way to Dirlot, which show that the material consists of sand and gravel, more or less stratified, with occasional blocks of conglomerate and sandstone, measuring 3 feet across. Indeed, the sections closely resemble the kame series of the midland counties of Scotland. One of these ridges is specially noteworthy on account of its length, extending from the farm- page 31 house of Dirlot to Dalemore, a distance of nearly a mile. Its height varies from 20 to 30 feet.^*

From Dirlot westwards to Strathmore Lodge conical mounds and ridges rest on the plain of grey shelly boulder clay. They are not abundant, however, occurring only at intervals, and chiefly on the left bank of the stream. From this point to Dalnawillan Lodge, which is about eight miles up the strath from Dirlot, similar heaps can be traced. Towards the latter locality they become more numerous, and on the left side of the valley at Dalnawillan they are well developed. Here the moraines form huge mounds and ridges, excellent sections of which are exposed by the roadside and in the burn courses.

It is observable that the material gradually changes its character as we ascend the valley, for while towards the eastern limit it is sandy and gravelly, with distinct stratification, it becomes more compact, and the stones are not so well rounded near the head of the strath. Indeed, it approaches the type of moraine matter which is commonly met with in upland valleys. We are inclined to believe that the kamiform ridges near Dirlot mark the easterly extension of the later glaciers, for it is highly improbable that they are of marine origin, when no trace of similar deposits has been observed between this locality and the eastern seaboard. On the other hand, the fact that the mounds can be traced at intervals from Dirlot to Dalnawillan, where the material resembles ordinary moraine matter, indicates a probable connection between the different deposits.

The evidence supplied by these later accumulations is important, because they rest both on the reddish-brown boulder clay and the grey shelly drift. They steal across the surface of the shelly drift for a distance of three miles between Strathmore Lodge and Dalemore, so that there can be no doubt that the shelly drift is of older date than the deposits under consideration. This is the only locality where we found the shelly boulder clay overlaid by gravel ridges and moraines; indeed, so far as our observations went, page 32 there is a marked absence of such accumulations throughout the area occupied by this deposit, as noted by Mr Jamieson.

Between Dalnawillan Lodge and Altnabreac Station, we observed moraine heaps composed of the same material as the mounds at the former locality. Over much of the moor also there is an irregular covering of gravelly material exposed in pits, which may belong to the same series. In Strathmore we observed the same material in places where no mounds could be seen, which leads us to believe that this covering may have been deposited by flood waters from the melting ice.

Again, on the moor to the west of Loch Shurrery, moraine heaps occur, and by the roadside leading to Loch Scye pits have been dug in coarse gravelly and rubbishy material, which evidently belongs to the same formation.

In the Braxside burn, which drains the western slopes of Ben Rah, south of Reay, moraines may be seen extending across the valley, and they occur at intervals on the moor northwards to Sandside. But to the west of Reay, in the direction of the county boundary, similar deposits are irregularly distributed over the slope. They increase in number and in size on the col and along the slope towards Strath Halladale, in the county of Sutherland. Indeed, the deposits of the later glaciation in this strath are grandly developed. The bottom and sides of the valley are covered with groups of moraines, displaying at some points a marked concentric arrangement. Numerous blocs perchés are strewn on these mounds, composed of granite and granitic breccia. The material consists of a compact stony and rubbishy matter, gravelly in some places and clayey in others, with sub-angular and rounded stones, few of them being striated.

Now, it is interesting to note that while the traces of the later glaciation overlap on to the grey shelly boulder clay at Dirlot, they do not reach the outer limit of the red boulder clay at Reay. Taking Shebster as the boundary line between the two boulder clays, the later morainic deposits "tail off" about three miles from this limit. But when we think of the large tract of country between Reay and Strathmore over page 33 which these deposits are spread, it will be readily admitted that they form an important feature in the history of the glacial phenomena of Caithness. Moreover, if we take into consideration the physical features of the north-west part of Caithness, the absence of deep valleys, and the limited elevation of the hills, we can hardly escape the conclusion that these later accumulations were deposited by a more or less continuous sheet of ice.

It is rather remarkable that, while these traces of the later glaciation are so abundant in the north-western part of the county, they should not have been observed in the large valleys in the south-east. We traversed the course of the Berriedale Water from the slopes of Maidenpap (2313 feet) to the sea, and observed no indications of moraines on the boulder clay slopes. It is possible, however, that small moraine heaps may yet be met with in the higher reaches of the Langwell, Berriedale, and Glut Waters.