408 ARRAN. GEOLOGY. OVERLYING ROCKS. 



nected by a common bond of mutual transition ; and with 

 respect to the latter, they all possess the double relation 

 of intersecting them in the form of veins, and surmounting 

 them in that of overlying masses ; the same portion pre- 

 senting both characters in connexion. 



I shall now point out such localities of the trap rocks 

 as are in any way interesting. 



The mass of greenstone incumbent on the sandstone 

 between Lamlash and Brodick bays, consists principally, 

 if not entirely, of that variety described as containing 

 augit and mesotype, and is properly therefore, an example 

 of augit rock. The same variety occurs at Clachland 

 point, along the shores of Whiting bay, and beyond that, 

 towards Kildonan Castle ; being in all these places found, 

 both in an overlying position, and in the form of irregular 

 masses intruding among the sandstone strata. At Kil- 

 donan a considerable extent of trap is to be seen ; various 

 in its aspect and structure, and forming a range of high 

 cliffs ; the shore itself presenting one flat bed, of which 

 the surface is even, and divided into polygonal compart- 

 ments. At the Bennan head, a similar cliff is to be 

 observed, but of less extent; and here, as far as the 

 ground will admit of observation, the whole mass seems, 

 at one side at least, to pass through the sandstone strata 

 which are found abutting against it : this mass is probably 

 a large vein. 



Masses of fine and coarse greenstone are found every 

 where dispersed among the hills in the interior of the 

 southern division of the island ; but for the reasons already 

 given, neither their true nature nor their extent can be 

 assigned. They may either be veins or overlying bodies : 

 in all probability both occur. The most continuous range 

 of greenstone which I observed, is to be seen in the hills 

 that divide the course of the remote parts of the Sliddery 

 water from the Brodick and Shiskin road, where these 

 rocks occupy a space of some miles in extent, but where 

 their boundaries or connexions with the other rocks, cannot 



