26 Geology of the Country [July 



From the Bungalow, going to the only accessible side of the rock, all 

 the blocks fixed in the soil are gneiss. In the enormous masses form- 

 ing the rock, this gneiss is entangled often in the thick veins of por- 

 phyry, which burst up through this primary stratified rock; the dia- 

 gram No. 5, represents this striking intrusion of the porphyry through 

 the gneiss. 



Owing to the contrast between the colour of the traversing, and of 

 the traversed, rock, these porphyry dykes are seen even from a distance ; 

 diagram No. 6, represents a hill, not two miles west of the Bungalow, 

 seen through a powerful telescope. 



Polliapolliam. — The country between Sanklydroog and Polliapolliam 

 is level ; and the whole of the protruding rocks, gneiss, which forms the 

 bed of the Cavery at this place, all the masses jutting in the river being 

 of that rock, analogous to the gneiss forming the bed of the same 

 river at Seringapatam (No. 92). 



Avanashy. — The rocks seen in the nullah near the magnificent 

 Pagoda, celebrated for its sanctity, close to the Bungalow are of a stra- 

 tified rock ; quartz being almost the only mineral forming it, with very 

 little hornblende and felspar. 



It is, undoubtedly, one of those immense veins of quartz which tra- 

 verse the hornblende slate formation; an anomaly in composition, 

 which sometimes happens in the same rock, when another of the mine- 

 rals composing it, the hornblende, forms strata by itself, to the ex- 

 clusion of the other components (No. 93). 



The stratification of the rock being quite evident, and the horn- 

 blende in such small proportion, we might be induced to call it sienitic 

 gneiss ; but, considering that the outskirts of the Neilgherries, as well 

 as the plain for miles round, have hornblende slate for surface rock, I 

 class under this last formation the rock at Avanashy. 



All the buildings attached to the Pagoda are constructed of this rock, 

 which contains imbedded nests of hornblende. 



Mottipollium. — Near Mottipollium, and as we approach the Neil- 

 gherries, the hornblende is seen, not, as hitherto, forming elevations and 

 hills, but only clustered masses jutting above the soil. 



As in other localities, it contains veins of quartz and felspar, numer- 

 ous pieces of which, when the imbedding rock decays, are scattered on 

 the soil— close to the ferry of the Bowhany river, at Mottipollium, I 

 found some boulders of granite, the felspar of which is reddish, 

 containing abundance of mica (No. 94). 



A few yards south and near the ferry, there is a knoll of a kind of 

 atalactitic iron ore (No. 95) j and in the plain I picked up a loose piece 



