324 



GEOLOGY OF BUTE. 



Limestone. 



137. The limestone of Kilchattan Bay is subordinate to 

 the sandstone; the strata of the two rocks are conformable, 

 and the dip nearly south at a moderate angle. At the 

 summit of the ridge, near the picturesque ruins of the 

 ancient castle of Kelspoke, the sandstone over the limestone 

 is seen dipping under the trap which bounds the rugged 

 terraced ridges, descending towards Garrochhead on the 

 south coast. These ridges have the same inclination south- 

 wards as the underlying sandstone strata, and present a 



Fig. 40. 

 a,b, Sandstone; c, limestone; rl, trap. 



succession of bold fronts towards the north. The sandstone 

 appears to have had its present inclination when the sub- 

 marine lava streams, of which these ridges consist, were 

 poured out over it; the scarped fronts were no doubt formed 

 by the action of currents when the land was rising. The 

 arrangement of the strata at Kilchattan is shewn in the 

 annexed cut (fig. 40). No fossils were found in the limestone. 



Dikes and tJieir Effects. 



138. The dikes of Bute are composed of greenstone or 

 basalt, and are very numerous, especially on the east coast. 

 They traverse the strata in various directions, and in some 

 cases can be traced for several miles continuously, preserving 

 nearly the same width and direction throughout. Two or 

 more are sometimes seen to meet and coalesce for some 

 distance, and again to separate; a narrow dike branches 



