654 Notes, chiefly Geological, [No. 165. 



From the base of the Ghauts by Lalpett to Arcot. From the base of 

 the Ghauts by Lalpett to Arcot, the formation is similar. The bold 

 ridge of Paliconda is chiefly of the variety of granite termed " Syenite,", 

 or a granite in which mica is replaced by hornblende, and in which 

 usually a reddish felspar forms a prominent ingredient. Its structure 

 in this mountain mass is both close-grained and porphyritic, and it is 

 penetrated by several dykes of basaltic greenstone having a general 

 N. and S. direction, but throwing off ramifications at nearly right 

 angles. Eurite is met with in veins near the summit on which the 

 pagoda stands. Dr. Benza appears to suppose the granite of Paliconda 

 of posterior origin to that of the Ghauts ; but as his opinion is grounded 

 entirely on Lithological difference, and its association with eurite, basalt 

 and porphyry, the age of which has not yet been determined, and which 

 are moreover equally associated with the ordinary granite of S. India ; 

 we must hesitate before hastily admitting this hypothesis in absence of 

 the other more decisive proofs of the age of Plutonic rocks derived from 

 disturbance or non- disturbance of strata of ascertained age, with or 

 without alteration, superposition, &c. 



Poni. Near Poni, and Mymundeldroog a few miles to the N. E. of 

 Vellore, granite still prevails, running in a broken chain of rocks up to 

 Chittoor, and tilting up the hypogene schists. At Lalpett, between Poni 

 and Arcot, is a ridge east of the Bungalow, having a S. westerly direc- 

 tion, and evidently an outlier of the great ghaut line of dislocation 

 which sweeps in a curve from Naggery by Raj, and Chellempollium, to 

 the Moogli and Sautghur Passes. The short ranges between Arcot 

 and Vellore, those of Paliconda, Vanatedroog, and Javadie on the 

 eastern flank of the beautiful vale of Amboor, are all equally subordinate 

 to this line of dislocation. Through them by transverse gaps the 

 Palaur, having traversed the longitudinal wall of Amboor, and the Poni, 

 after having irrigated that extending from Chittoor to the N. bank of 

 the Palaur, find their way easterly to the plains of the Carnatic. 



The summit of the Lalpett ridge is crested with bare blocks of a 

 dark massive hornblendic rock ; but the great bulk of the hill is com- 

 posed of gneiss penetrated by dykes of basaltic greenstone and granite, 

 great disturbance in the strata is observable. Towards the N. extremity 

 of the hill the gneiss is scarcely to be distinguished from the granite, 

 except where large surfaces are exposed. The granite often passes into 

 pegmatite. In some blocks I found the dull olive-green mica replaced 



