890 
Proceedings of the Royal Society 
That the striations on rocks were produced by an agent, the same 
as, or similar to, that which caused striation on boulders, is evident 
from the multitudes of cases where there are striated boulders and 
striated rocks close to or near one another, the direction and 
appearance of the striae on both being generally the same. 
Great numbers of rock striations occur in the Hebrides, most of 
which are described in the Fifth Report. Thus (at p. 816) an account 
is given of smoothed rocks at Jocdar, on which there are twelve or 
fourteen deep ruts, some of them 4 or 5 feet in length. One 
measures 8 inches across and 2 inches in depth, and there are others 
of similar width and depth,— the ruts being in all cases deeper and 
wider at their west than at their east ends. In the Lewis^ at TJig and 
Carlowrie {Ahstmd^ p. 819), similar cases occur; also Kilmory 
[Abstract, p. 780), Buteshire [Abstract, p. 791). 
These rock striations are found not only on surfaces more or less 
horizontal, but also on surfaces which slope, and even on surfaces 
which are vertical. 
As examples take the two following cases — 
1. In Bute, there is a rocky defile, about 30 yards wide^ at Barone 
Hill [Abstract, p. 793), through which boulders and drift materials 
have evidently passed. One side of this defile presents extensive 
smoothings, on which there are ruts, some of them 1 2 feet in length, 
and more deeply cut into the rock^ at the end where the striating 
agent entered the gorge, viz., the N.Wd The direction of movement 
is farther shown by the fact, that from that end the ruts slope 
ujpwards at angles of from 20° to 30°, the result, no doubt, of the 
force with which the materials were pushed or driven through the 
gorge [Seventh Report, p. 19). 
2. Another example occurs on the West side of Arthur's Seat, 
Edinburgh, as explained in Abstract, p. 843. Boulders and other 
drift materials had passed through this gorge, which is only 
about 10 yards wide. A boulder sticking on one of the sides was 
striated on its exposed side. One of the rocky sides also presented 
numerous striations, — some of them 6 feet in length, and J of an 
inch deep. At the narrowest part of the defile, where there would 
be the greatest difficulty in forcing a passage, the striae are rising 
up at an angle of 4° or 5° from the end where the materials had 
entered the defile. 
