284 Proceedings of the Royal Society of Edinburgh. [Sess. 
appearance suggests that they had all at one time been embedded in the 
clay, but had been washed out of it by a current which was not powerful 
enough to roll and round them, but only to scrub them with the smaller 
particles washed out of the clay. 
That the clay had great tenacity is shown by the position of the largest 
0 & / 2 3 4 S 6 7 8 3 lO // /2 INCHES 
1 , I i I . I . \ _A I 1 1 1 I . I ■ I I I 1 I I 1 1 1 
r r " rTT ", 1 » 1 » 1 » 1 T 1 1 1 T 1 1 r 
O 20 40 80 120 160 200 240 280 320 MM. 
Fig. 7. — Striated Boulder of Red Sandstone. The embedded portion plain, the 
exposed part hatched. A, side on ; B, end on. 
boulder, which though only slightly embedded and almost on edge, had not 
toppled over. 
Fourteen of the stones are from sedimentary rocks. Of these, six almost 
certainly belong to the Old Red Sandstone formation as developed in 
Sutherland, Caithness, Orkney, and Shetland. The largest of these 
(12 x 7J x 2f inches) and a smaller one are of a dark, reddish-brown fine- 
grained hard micaceous sandstone, like some members of the Brenista 
flags of Southern Shetland (text fig. 7). Two small well-glaciated frag- 
ments of grey flagstone are identical with the well-known “ Caithness 
flags” of Caithness and Orkney. The remaining specimens are of red 
