ARRAN. GEOLOGY. OVERLYING ROCKS. 403 



be traced all along the shore. I did not there discover 

 the sandstone below it, and I cannot therefore determine 

 whether it is in the form of a vein or an overlying mass ; 

 an object of no consequence in a scientific view, as it 

 was just shown, that, at Drumodune, it exists, like the 

 other varieties of felspar rock, in both these states. This 

 rock can be traced to a considerable distance inland ; but 

 its connexions and boundaries are there as obscure as those 

 of the other rocks already described. I must add that, 

 throughout this porphyry, irregular concretions and im- 

 perfect veins are occasionally to be found, consisting of 

 the base alone, void of crystals, and on a first view resem- 

 bling ordinary trap veins : an appearance very analogous 

 to some of those well known veins and concretions that 

 occur in certain granites. 



Thus far only does it appear necessary to describe the 

 overlying rocks of the felspar division which occur in the 

 island ; any further attempts at individual description would 

 only lead to a fatiguing repetition, without benefit to the 

 science, or utility to the geologist who may hereafter 

 traverse the same ground. The veins however, pre- 

 sent somewhat more variety and greater interest ; while 

 it is at the same time more easy to refer to their places ; 

 the most conspicuous being tolerably well indicated by 

 geographical marks. 



One of these veins is to be seen on the shore near 

 Corygills, between Brodick bay and Clachland point. 

 From the manner in which it appears in the cliffs, it is 

 on a first view scarcely distinguishable from the sandstone 

 in which it is enveloped, and has indeed been described 

 as a white columnar sandstone. On comparing its posi- 

 tion however with that of the sandstone, it is easily seen to 

 be a vein placed at an angle with that of the strata in which 

 it lies ; its dip being towards the south, at thirty degrees 

 or more, while the surrounding sandstone is placed at a 

 much lower angle. It is about thirty yards in thickness. 

 It consists of a pale yellowish white clinkstone, at times 

 slightly porphyritic, and exhibits two distinct structures ; 



