49 



no economical value. The Kilchattan beds are of the same age ; 

 they are subordinate to sandstone and without fossils, but being of 

 considerable thickness, they have been extensively quarried. 



36. But there are in Bute sandstones and limestones newer 

 than these, which have been till very recently quite overlooked 

 by geologists. There occurs, in fact, hanging on to the flanks of 

 the old red sandstone at Ascog, a small coal formation, a portion of 

 the lower marine series. This was lately discovered and identified 

 by means of its fossils, about the same time, and independently of 

 one another, by Mr. James Frazer of Glasgow and the writer of 

 these notices, and may yet turn out to be of economic value. It is 

 connected with an isolated overlying mass of trap appearing on the 

 shore, and occupying the cliffs near Ascog mill. On the north side 

 of the promontory, south of the mill, several thin courses of nodular 

 limestone traverse beds of brown coloured crumbling shale subordi- 

 nate to sandstone. The shale is of considerable thickness and rises 

 into banks above the road. The south side of the promontory pre- 

 sents the following section : 



(a) Limestone; (6) shale with thin coal seams; (c) limestone breccia; (d) trap. 



The lowest bed (a) is a fine grained, bluish-gray, nodular lime- 

 stone. Over it is a bed of black bituminous shale (b), containing 

 veins of coal about a quarter of an inch thick ; and upon these rests 

 a bed of concretionary limestone (c), the base or paste being a dark 

 coloured limestone, and the concretions rounded lumps of the same 

 rock, often of considerable size. The upper part of the cliff is 

 occupied by trap in various prismatic forms. The base of the con- 

 cretionary limestone is so much altered by the contact of the trap, 

 that the two rocks can only be distinguished by the action of a 

 strong acid. A like change is produced upon the imbedded lumps 



