418 ARRAN. GEOLOGY. PITCHSTONE. 



surface an orange brown stain in the places where this 

 change of character occurs. 



The third vein is much more remarkable. This runs 

 in a S. S. W. course from the cliff for a considerable 

 space, till it is lost in the sea. It varies in breadth from 

 twelve feet to thirty, being slightly incurvated, and in 

 some places appears somewhat conformable to the sand- 

 stone; yet, even in these, it forms an angle with the 

 strata, dipping towards the east. The pitchstone of this 

 vein is of a dark green colour, and is somewhat porphy- 

 ritic, but variable in texture. Near the sea, it is accom- 

 panied on each side by a vein of chalcedonic chert, also 

 slightly porphyritic ; a circumstance much resembling that 

 which occurs in the pitchstone of Egg, the chert vein 

 there lying in the middle of the pitchstone. 



The fourth and last mass is also of considerable extent, 

 but is less easy of investigation. At first, nothing is 

 perceived but a confused heap of detached blocks : a 

 narrow examination however, shows that these are all 

 portions of a single mass ; the greater number of them, 

 although detached from each other, being still in situ. 

 This collection of fragments is horizontal or nearly so, 

 and seems to be the exposed portion of a vein, con- 

 formable to the sandstone, and split into separate parts 

 by exposure to the weather. In structure, it is perfectly 

 identical with the smaller mass first described; showing 

 the same gradual passage into chert, with the same orange 

 brown stains. 



On comparing these four separate masses, it seems pro- 

 bable that the first and fourth are portions of the same 

 vein, which in one place cuts the strata and in the other 

 conforms to them ; the identity of structure being abso- 

 lute. In the same way it seems probable, that the second 

 is a portion of the third, the intermediate connexion, in 

 both cases, being obscured by the incumbrances in their 

 vicinity. 



