1836.] 



Neelgherries and Koondahs: 



2G9 



tinguish it from the other three further on. The exposed portion of 

 this dyke, does not extend more than half a mile N. E. of the rivulet, 

 as its outgoings show clearly. Its texture is very compact and tough ; 

 fracture glimmering (No. 88). Following the outgoings of this basalt 

 eastwardly, about a hundred yards further up we see many of them 

 decomposed, through their whole bulk, into the so often mentioned 

 yellow ferruginous clay ; while in others the decomposition has not 

 penetrated so deep (No. 89). What the thickness of this dyke is, can- 

 not be ascertained, its lower portion being under water. Above this 

 dyke the numerous projecting masses, at the foot of the hill, are all 

 sienitic granite (No. 90), which occupies also the hills on the S. W. 

 of the rivulet. 



On ascending to the summit of this hill, which extends in the usual 

 rounded form eastward, we see that it is entirely formed of basalt, 

 in a dyke probably a diramation of that of the rivulet, and extends 

 all along the small ridge for nearly a quarter of a mile (No. 91). 

 This dyke is thicker than the former one ; many loose masses, de- 

 tached from it, lay scattered along the ridge of the hillock, and on 

 the small eminence near the road. Descending the north declivity 

 of this same hillock, the masses on its surface are sienitic granite, and, 

 at the foot of the other side, basalt again appears. So that it appears 

 that these three dykes, or, more probably, three ramifications of the 

 same trunk, have entangled the sienitic granite of this hill betwixt 

 their diramations. 



Proceeding still north after about tw T o hundred yards, we meet with 

 another dyke, through which the road has been cut, and, judging by its 

 proximity and direction, this perhaps is also a branch of the same 

 trunk, as the others in the first hill. Its direction is the same, 

 but the dimensions in this last are on a larger scale. In this dyke 

 the basalt is more compact and has a duller fracture (No. 92) ; 

 although in some parts it is glimmering, on account of the usual admix- 

 ture of small microscopic crystals of augite (No. 93). This dyke has, 

 at its western extremity, that is near the road, a breadth of three 

 yards; of course, I am speaking of the trunk, because, as it ad- 

 vances eastward, it gives out numerous ramifications, shooting in all 

 directions, one of which branches off nearly at right angles with the 

 trunk, and traverses the eastern termination of the little ridgy sum- 

 mit of the second hill (No. 94) ; and it is near this transverse branch, 

 that the sienitic granite contains, in some blocks, large crystals of 

 foliated hornblende (No. 95). It is impossible to give an adequate 

 idea of the intricate, net-like ramifications of this fourth dyke through 

 the sienitic granite, in all possible directions, entangling occasionally 

 numerous pieces of it, and at times insinuating itself, strata-like, in its 



