Chap. I.] 



ECONOMIC GEOLOGY. 



203 



feet in length, and 2 or 3 feet in width and F'^- 21. Quarrying tools 

 thickness, are obtained with the expenditure 

 of a considerable amount of labor, and if re- 

 quisite, are afterwards roughly trimmed with 

 hammers on the spot, and then transported 

 to the required locality on rude buffalo carts. 

 Regular excavations are rarely opened for 

 quarrying purposes. In general the stone 

 is obtained from some rocky ridge, the soil 

 being previously sounded with a crowbar to 

 ascertain the existence of a block at no 

 great depth, the stone is uncovered and 

 detached, and the hole abandoned, to be filled 

 with rain and mud on the first heavy down- 

 pour. Thus the outcrop of a band of lime- 

 stone may be frequently traced by the row 



of little pits, left by the native quarrymen ; ^' ^^^^^^ ^^ Chi«el. 3, Stone 



mallet. 4, Iron wedge. 5, 

 although no rock is perceptible at the (.^.^^^^^,_ g^ 7^ Trimming 



surface. hammers.— 



Gneiss and trap are the most durable stones obtainable for those parts 



of buildings that are exposed to the weather. The 



latter is but little used, as it occurs only in a few 



dykes in the neighbourhood of Ootatoor and Volcondahpuiam, and owing 



to its extreme toughness, is only obtainable with great labour by the 



native method of working. Judging from the almost inappreciable 



extent to which exposed blocks of this stone have been affected by the 



weather, it must claim pre-eminence, in point of durability, over all 



other materials except perhaps some of the Quartzo-felspathic varieties of 



the gneiss, the permanence of which is attested by the great rounded tors 



and bossy hills of this rock scattered over the country, and also by the 



delicate carvings of some of the pagodas, notably those at Tanjore, 



Gneiss and Trap. 



