460 Dr. Mac Culloch on Quartz Rock, 



similar investigations well know how difficult it is to ascertain the 

 disposition of large tracts of country unless observed from situations 

 so elevated as to raise the spectator above all the obstructions which 

 the varying forms of high ground throw in the way of this great 

 natural perspective. The remarks of Saussure on the highest 

 summits of the Alps, which relate to this subject, are well known. 

 It is not material to the purpose of determining their stratified 

 structure, whether this stratification be continuous for a large space 

 or whether it be various and interrupted ; however desirable it might 

 otherwise be to ascertain its disposition over the whole extent which 

 these mountains occupy. From the low positions in which I was 

 compelled to view those strata which I saw at hand, they appeared 

 to be in some places horizontal, in others occupying various angular 

 elevations, sometimes inclining to the north, and sometimes in a 

 direction the very reverse. Such perhaps would also have been my 

 opinion of the strata of Jura, had I not attained its highest summits. 

 Future observers who shall ascend the Cuniack hills, the Sugar-loaf 

 mountain, or Ben More, wull be able to ascertain what I have left 

 undone. Want of roads, want of horses, want of population, want 

 of every thing, render this country among the most impracticable of 

 Scotland, 



The nature of this rock is exceedingly various. It is often a 

 compact stone of a yellowish colour, and uniform texture, resembling 

 a granulated quartz, simple in its composition, and breaking with an 

 imperfect conchoidal fracture. Occasionally it assumes a coarser 

 and looser texture, and in these cases the weathered surface becomes 

 white, and acquires a harsh and sandy feel and aspect. However 

 uniform the fresh specimens appear when broken, they almost 

 invariably disclose some internal mechanical arrangement on weather- 

 ing, which betrays the nature of their original formation, a circum- 



