Mr. Bryce on the Geology of the Island of Bute. 



203 



4.) Tho lower limit is a projection or tongue, running off from the 

 principal mass, and descending to the shore, where it rests on a limestone 

 breccia, as already noticed. At other parts it rests on sandstone, the 

 line of junction ascending rapidly as it retires from the shore on either 

 side, to the south and west. The manner of this approach is shown in 

 tho annexed cut, which is a map or ground plan, and not a section. The 

 extent inland is somewhat less than a mile. 



a, sandstone ; b, c, shale and limestone ; d, trup ; e, e, beds of lignite ; r, road cut 

 through the projecting mass of trap. 



These trap rocks derive their chief interest from being the repository of 

 beds of lignite, — a substance so rare in Scotland that I believe no well 

 marked beds occur on the mainland, and only two or three on the other 

 islands ; and these far up on cliffs nearly inaccessible, in Mull and Skye. 

 I was led to a careful examination of this carbonaceous deposit, and the 

 associated beds, by the statement of Dr. MacCulloch, that some of the 

 strata which occur at this place were unlike any he had seen in his sur- 

 vey of the western islands. 



The principal bed is situated in the face of the cliffs above the road, a 

 little to tho south of Ascog mill, as shown in the annexed section, (No. 6.) 



No. 6. 



s, sandstone ,• r, terrace and road; f, f, greenstone; a, trap-tuff; b, red ochre; c, %- 

 nite bed ; d, pisolitic ochre ; c, porphgritic amygdaloid, the upper portion much altered. 



