772 Notes, chiefly Geological, [No. 166. 



Chennamulla. — From Erode to Chennamulla a number of rocky 

 undulations are crossed, running parallel with the strike of the strata 

 nearly SSW. The formation is gneiss alternating with mica, and 

 hornblende schist, with layers of actynolitic schist. The dip is gene- 

 rally E. 15° S. 



The hill of Chennamulla is a mass of stratified quartz sprinkled 

 with garnets and passing into garnet rock. Some of the imbedded 

 garnets are tolerably well crystallized, and of deep rich colour. The 

 prevalent form of crystal is the dodecahedral, the rhombic dodeca- 

 hedron (Almandine) is not so common. The gneiss is often coated 

 with incrustations of a flesh-coloured kunker: and beds of it form 

 in many places the subsoil. The surface soil is in general reddish and 

 gravelly. 



At the foot of the rock I picked up a fine garnet imbedded in a nest 

 of a dark fibrous hornblende. 



Beryl mines of Konghyum. — From Chennamulla I visited the Beryl 

 mines of Konghyum, of which a description has been already given 

 by me in Jamieson's Philosophical Journal. 



I shall now content myself by pointing out, that they lie close to 

 the village of Poddioor in the Konghium Taluk, about forty miles 

 ENE. from the town of Coimbatore, which lies in 11° N, and 77° 1' 

 E. It occurs in the vicinity of granitic, porphyritic, and pegmatitic 

 veins in the gneiss, associated with fine specimens of rock crystal 

 Cleavelandite, and, though rarely, pyramidal felspar or scapholite. 

 Konghium was the ancient name for the Coimbatore district. 



Avenashy. — Gneiss, and hornblende schist penetrated by granite 

 and basaltic greenstone, are the rocks next within the plain around 

 Avenashy. Dip of strata, E. 10° S. strike N. 10° W. Soil and sub- 

 soil similar to those of Chennamulla. Saltpetre is here manufactured 

 from a mixture of old village refuse with the rich vegetable soil dug 

 from the bottom of a tank. Patches of the ordinary soil are seen 

 moist with impregnations of soda. The staple articles of produce are 

 juari, raggi, and bajra. Cotton is grown at a little distance in the 

 regur plains. Cotton cloths are here manufactured. 



The village is pleasantly situated in the plain at the base, and within 

 view of the towering peaks of the blue mountains; it was anciently 

 a place of note, but has decayed latterly, and the Kusbah is transferred 





