2 INTRODUCTORY REMARKS. 



only of the western coast, but of the leading vallies and 

 ridges of Scotland. An analogous disposition will be 

 found to prevail in these islands ; and the variations, 

 whicih occasionally amount to a few points on the con- 

 tinental shore, will receive illustration from circum- 

 s r -E,nce& that will come under review in giving the details 

 of the individual islands. These bearings of the coast 

 and of the ridges of hills, will be seen, in most cases, to 

 follow the directions of the strata, as will be exemplified 

 in Sky and in many other places ; although in a few, as in 

 Bute for example, there is a want of this coincidence. 

 I must here remark generally, that the imperfections of 

 the Map form a source of occasional error and render it 

 difficult to ascertain the general bearings, whether 

 of the land or the strata; a defect which there is no 

 immediate prospect of removing. Examples in illustration 

 of this remark will occur in the course of the investigation. 

 To what extent the description of these Islands may assist 

 in laying a foundation for determining the general structure 

 of the Highland district, is a question that involves con- 

 siderations too numerous to admit of a definitive answer. 

 We may expect, that in a certain degree similar rocks 

 will be found on the prolonged bearings of those which 

 have been ascertained; and, as far as my observations 

 have gone, such continuations can be traced over a 

 space, at least sufficient to regulate considerably the 

 plan of any geologist, who shall pursue the investigation 

 of the neighbouring main land *. Causes, too well known 

 to require mention, limit the assistance to be derived 

 from this circumstance; yet, when the Islands shall 

 have been described, it will be seen that a considerable 

 step has been gained, and a point of departure fixed for 

 the future examination of the Highland and mountainous 

 division of Scotland. 



* While this work is passing through the press, I am in the act of 

 verifying the truth of this conjecture, by an extensive examination of the 

 western coast. -Sept. 1818. 



