1336.] between Madras and the Neilgherries, 19 



granite of primary formation, which contained hornblende instead of 

 mica. By reasoning of this strictly scientific character, to avoid con- 

 fusion, he proposed the term sienitic granite for the primary rock, re- 

 serving that of sienite for the overlaying rock, which is associated with 

 porphyries. 



As far back as 1813, Brongniart, in his classification of rocks, ad- 

 mitted the sienite granito'ide, which is synonimous with sienitic granite. 

 Humboldt, in his Essai geognostique sur le Gisement des Roches, not 

 only recognized the essential difference of the two rocks (the one an 

 overlaying rock of posterior origin to the other, which he clearly 

 states to be a true primary granite, with hornblende instead of mica), 

 but he was the first to point out the mistake of Werner, who thought 

 the Dresden rock to have the same geological position as that of 

 Egypt. 



From Europe let us pass to the writers of this country. Voysey 

 adopted the name of sienitic granite in the same sense as the proposer 

 of the term. Mr. Hardy (see his geology of Udayapoor) writes as 

 follows : " the granite there is the true granite, viz. quartz, felspar and 

 mica ; sometimes this last is wanting, and then it passes into pegmatite, 

 and then into sienitic granite ; then into hornblende rock> some kinds 

 of which resemble the green-stones of the trap formation." 



This limited signification of the term sienite is perfectly correct, 

 when applied to the rocks in some of the localities of southern India; 

 the rock being there often associated with porphyries, as I have had 

 more than one opportunity of observing at Tripatoor, Pallicondah, &c. 

 where porphyry and eurite accompany it. 



Many of the blocks scattered in the plains, between the foot of the 

 hill and the Bungalow, are sienitic porphyry (No. 62), having well 

 defined crystals of felspar, imbedded in a paste of hornblende, differ- 

 ing in this from the porphyry of Tripatoor (to be described hereafter), 

 the paste of which is compact felspar. 



Level with the soil, and near the skirts of the hills, there are nu- 

 merous outgoings of basaltic dykes, decomposing in concentric layers 

 (No. 63). 



Proceeding to the foot of the hill the sienitic porphyry assumes the 

 structure of true sienite (No. 64), that is, an uniform mixture of horn- 

 blende, felspar and quartz, not in regular crystals, which both in Europe 

 and in America is associated with basalt, eurite and other trap rocks ; 

 this is also the case with this rock of Palliconda. As we ascend the 

 hill we see the same rock, sometimes with a porphyritic, and at others 

 with a granitic, structure. Indeed the transition between these two 

 appearances is quite insensible, and often seen in the same block. 



Dykes of basalt are found traversing this sienite, their direction being 

 ("at least of all I examined there, more than six in number) uniformly 



