M k. Bryce on the Geology of the Island of Bute. 201 



lumps of tho same rock, often of considerable size. The upper part of 

 the cliff is occupied by trap, in various prismatic forms. An interesting 



No. 3. 



a, limestone; b, shale, with thin coal seams; c, limestone breccia; d, trap. 



change has been produced by the contact of the trap. The base of the 

 concretionary limestone has been so much altered from its original state 

 as closely to resemble the trap itself. So complete, indeed, is the meta- 

 morphosis, that the two rocks cannot be distinguished but by the action 

 of a strong acid. The imbedded lumps have undergone a similar change, 

 particularly in the upper part of the bed. This trap rock occupies a 

 considerable area, inland ; and is 100 to 200 feet thick. Speaking of it, 

 Dr. MacCulloch says, — " When examined on the shore it appears rather 

 to pass through the sandstone than to lie over it ; but there is consider- 

 able obscurity in this place, as the lateral junction of the two is concealed 

 by a cavity filled with earth." The section of the coast is better exposed 

 at present, probably in consequence of the continued action of the sea ; 

 apd there can be no doubt that the relative position of the strata is such, 

 throughout, as is given in the preceding section, (No. 3.) The trap 

 reposes upon the sandstone, and does not pass through it. 



5. The most considerable mass of limestone on the island is that 

 which occurs on the south side of Kilchattan bay. Its characters are 

 accurately described by MacCulloch, but he has fallen into a slight error 

 with respect to its position. " This bed seems to lie above all the sand- 

 stone strata at this place, and to be the rock immediately in contact with 

 the superincumbent trap." The annexed cut, (No. 4,) shows the true 

 position of this bed of limestone, ascertained by a careful examination of 

 the ground. 



At some distance above the limestone quarry, near the ruins of the 

 ancient castle of Kolspoke, the beds of sandstone, 6, are distinctly seen 

 dipping towards tho trap, both the dip and the inclination being the same 

 as below the limestone; and it honce appears that the limestone is here, 



