168 On the Granite formation 



and then again similar portions of syenite, as if half melted, 

 may be seen fining out, and mingling into veins of the mass ; 

 and it is not uncommon to see in a vast mass of granite 

 a mixture of veins, fragments of syenite, of hornblende 

 slate, of quartz veins, granite veins, and portion of gneiss, 

 contorted and mixed together in a degree of complete con- 

 fusion, which might emulate, if not surpass, that represented 

 by McCulloch in Cape Wrath (Western Isles.) 



Where the granite is of a dark colour, from containing a 

 larger proportion than common of hornblende, the rock has 

 then the appearance of being intersected and striped by 

 white veins, which contain sometimes so little hornblende 

 as to approach to a pegmatite. 



As small portions of a perfect gneiss are found in the 

 mass of the granite, caused by the parallelism of the veins, 

 so also in the vicinity of granite masses a perfect gradua- 

 tion may be seen between the granite and masses of gneiss ; 

 which are perfectly and largely lamillar in structure, and 

 which is most commonly seen between the junction of the 

 schistous series which form the plains with the granite 

 ranges. 



On the round surface of many of the large masses of 

 granite, both at the level of the plains and on the highest 

 summits, pointed oval-shaped cavities are found, often of 

 great size, sometimes (as at Anchitlydroog,) 30 feet in length. 

 Half a mile east of the base of the Royacottah hill is a large 

 mass of granite, in which a great number of these cavities, 

 between two and three yards in length, may be seen, and 

 where the structure of the rock is very plainly shewn ; they 

 are caused by the disintegration of portions of friable gneiss, 

 which have been embedded in the structure of the rocks, 

 and which may be seen by the portions still remaining to 

 have been blended into the veined and waving structure of 

 the granite. It is remarkable, that the direction of the 

 longitudinal axis of these cavities is generally north and 



