156 



GEOLOGY OF ARRAN. 



suspected. The surface is traversed by a series of wavy 

 lines, conforming to one another throughout. This indicates 

 a laminar arrangement within; and it is along these lines 

 that the rock splits completely up in the advanced stages of 

 decomposition. 



The relations of these various igneous products is further 

 illustrated by another dike, which occurs a little way up this 

 river. A great vein of claystone crossing the bed of the 

 stream shews a distinct passage into jaspery hornstone. The 

 jasper and chert veins in the Tormore pitchstone, with 

 associated claystones and basalts, place these same relations 

 in a very clear light; and when we view the appearances 

 which they exhibit in connection with those now described, 

 we cannot hesitate to admit that all these products of fire 

 blend into one another, the varying aspects which they 

 assume being due to a slight change in chemical com- 

 position, in molecular arrangement of parts, or in the rate 

 at which they were consolidated from a state of igneous 

 fusion. 



Fig. 30. 



The microscopic structure of the Arran pitchstones has 

 been recently examined by Zirkel of Leipzig (Zeitschrift der 

 Deutscken GeoL Gesdl 23rd Band., Jan. 1871) and by Mr. S. 



