Chap. V.] trichinopoly district — ootatoor oroitp. 63 



close-packed limestone masses. Towards its base no definite structure is 



perceptible, the great protruding hummocks being pitted and honey-combed 



into a variety of irregular forms by the action of the weather, but in the mid- 



^ die and upper parts a very distinct bedded structure 

 Bedded structure of i. l i. j 



upper part. jg manifested in the arrangement of the masses, al- 



though there is no corresponding change in the mineral character of the rock. 



At the summit of the slope the rock disappears beneath regur, and a 

 short distance beyond this the Trichinopoly beds, resting on the limestone, 

 are seen wherever broken ground exposes the underlying rocks. The rock, 

 of which the greater part of the ridge is composed, bears a close resem- 

 blance to that of Tripatoor. The streaked coralli- 



JMincrtil ditiVtictcrs 



ferous variety is occasionally seen towards the base, 

 and elsewhere the rock is either white, or of a pale flesh or yellow color. 

 The first of these three varieties presents rather an earthy or chalky frac- 

 ture, and, so far as can be judged by the eye, unaided 

 Chalky variety. 



by chemical tests, would seem to be an almost pure 



indurated calcareous mud. This, however, is never seen in large masses, 



but only in the interior of blocks of the flesh color- 

 Flesh colored crystalline. . 1 • 1 • 1 1 IT 1 • 



ed variety, which is hard and sub-crj^stallme, being, 



in fact, the white rock altered by the infiltration of a calcareous solution. 



The third-mentioned variety is the most common, 

 Ochreous argillaceous. 



and this derives its color from the admixture of an 



ochreous clay, similar to that which occurs so largely in the bedded depo- 

 sits of the Ootatoor Group. In this variety, which occurs both at the 

 base and in the higher parts of the ridge, fossils are occasionally found, and 



sometimes a great part of the stone consists of com- 

 Comminuted shells. 



minuted shells. Close to the bottom a few pebbles 



of gneiss, apparently derived from the underlying boulder-bed, are occa- 

 sionally met with, but I have never obtained these 

 Pebbles in limestone. 



at more than a foot or two from the bottom, and 



throughout the upper part of the ridge I have never met with a single 



