Chap. VIII.] economic geology. 14-9 



other patterns. Among the useful articles may be mentioned watch- 

 g-lasses and double convex spectacle lenses for old or weak sight. Among 

 some specimens of Vellum stones^ cut and uncut_, presented to the 

 Museum of the Geological Survey of India by W. M. CaddeU, Esquire, the 

 Collector of Tanjore, was a crystal of amethyst, (a six-sided prism, 

 with terminal pyramids,) in which, radiating from the correspond- 

 ing faces of an internal pyramid, was a brush of small acicular crystals 

 of Rutile. The crystal, which was rather broken at one end, measured 

 one inch in length by 3*5 in diameter."^ These pebbles and crystals are 

 most likely derived, in the first place, from large quartz veins in the meta- 

 morphic rocks. 



The preparation of vessels of all shapes and sizes from blocks of 



pot-stone or compact steatite, has already been re- 

 Pot-stone vessels. 



ferred to (see note, page 102). The vessels are 



cut by means of various chisel-shaped tools, when resting either on a pad 

 of straw and rags, or else on the operator's lap. The profits seem to be 

 but very small, judging by the poverty-stricken appearance of the workers 

 at Tandacoundenoor, &c., which is due probably to the great number of 

 failures they have to contend with, owing to numerous flaws and impu- 

 rities in the pot-stone. The manufacture of vessels of pot-stone or com- 

 pact steatite is also carried on at Yermaputty, a village lying near the 

 western end of the great valley separating the KolymuUays from the 

 Tullamullay. In one pit at this place from which pot-stone had been dug, 

 we noticed a small vein of beautiful dark green crystalline Chlorite. The 

 vein varied from 1 to 4 inches in thickness. 



Trap Bochs are, within our area, used only as rough stones for tank- 



bunds, &C.J or as road metal, for which latter 

 Trappean rocks ; uses. 



purpose they are better than almost any other 



class of rocks, especially for military and other roads exposed to heavy 



* The specimens presented by Mr. Caddell were unfortunately lost in the ^vreck of 

 the "Aurora." 



( 371 ) 



