of Salem and Barramahal. 1 77 



in the basalt. Fifthly, there is evidence that the basalt was 

 not in motion ; because in the dyke at Deonhully, granite 

 veins parallel to the sides may be seen in the basalt in the 

 same way exactly as the basalt is in the granite; and in 

 the dyke at Boredurraputty a fine point of granite, about 

 twelve inches long, may be seen projecting into the dyke of 

 basalt, and as in no case are these dykes ever connected with 

 any mass of basalt, and as the proportion of their mass does 

 not exceed that of a million to one, as compared with the 

 granite, and as therefore no heat which they would have 

 afforded could have softened the granite, I therefore think 

 there is strong evidence of these dykes being but large 

 veins, cotemporaneous with the granite itself. 



At Namkull, however, in the base of the rock, there may 

 be seen a dyke of basaltic hornblende, about two feet in width 

 and many yards in length, which shews strong evidence of 

 having been run into the fissure in the solid granite, the edges 

 answering all along, and a piece of the granite separated in 

 the division, and now lying across the fissure, may be seen 

 exactly to answer to a contiguous cavity in the side. 



In the Boredurraputty dyke it is a curious fact, that the 

 dyke, which is about nineteen feet wide and runs exactly 

 north and south, may be traced on the surface of three 

 miles to where it is embedded among the schistous rocks 

 in the plain, and it is there changed into hornblende rock, 

 (black granite,) in globular masses. 



This might seem to prove the similarity between black 

 granite and basalt, as is generally believed ; but as the 

 granite which is hornblendic is not at all altered in structure 

 in the vicinity of the basalt, the hornblende preserving its 

 crystalline form and characteristic appearance, it is plain that 

 the basalt and hornblende cannot differ from each other 

 merely in the manner and rapidity of cooling, as is sometimes 

 supposed by Mineralogists, because both in this case must 

 have cooled at the same time. 



2 A 



