362 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 1, 



many places along the north-western coast of Sutherland and Eoss 

 to be surmounted by great masses of dull-brown, red, and chocolate- 

 coloured sandstone and conglomerate (h). This superposition is pecu- 

 liarly well exhibited in the lofty and pyramidal mountains of Coul- 

 more, Suilven, Coulbeg, Canisp, and Queenaig. When viewed from 

 a boat at sea, these relations are precisely as MaccuUoch described 

 them, and just as they are shown in fig. 1. But whilst their in- 

 ferior relations were long ago well known, it has only been recently 

 ascertained, as explained in the Introduction, that, as a whole, 

 these north-western conglomerates and sandstones lie unconformahly 

 subjacent to the series of quartz-rocks with fossiliferous limestone 

 (c^ c^ c^) as well as to the micaceous, gneissose, and chloritic schists 

 {d) which occupy so large a central portion of the Northern High- 

 lands. 



The conglomerate and sandstones of the North-west Coasts, which 

 occupy this low position in the geological series, and which have on 

 the whole a strike from N.IST.E. to S.S.W., are, in truth, similar in 

 lithological character to the purple and chocolate -coloured grits and 

 pebble-beds of the Longmynd, which in the earlier days of our 

 science were termed "Compound Sandstone" by Townson, and 

 which were subsequently described at some length by myself, when 

 I first showed that they formed the real base of all the Silurian 

 series of Shropshire and the adjacent counties (see ^ Silurian System,' 

 p. 253, pis. 31, 32, and ' Siluria,' new edit. p. 23). 



Fig. 2. — Mountains of the West Coast of Sutherland and Boss. 

 (From ' Siluria,' new edit. p. 198.) 



Canisp (2780 ft.). Suilven. Coul-more. 



These rocks, as they appear on the coast of Sutherland, have been 

 so truthfully and poetically described by Hugh Miller (though he 

 then, like myself, thought they were Old Eed Sandstone), that in 



