VOL. LXXXVIII.] PHILOSOPHICAL TRANSACTIONS. 359 



dispatch a load of the stone, in a day or 2, which I got at the pollam, with the 

 charge of it. The distance from this place, by Namcul, is 84 miles. 

 " 9 Tritchinopoly measures of the corundum stone weigh 50lb. 



p. f. c. 



14- Madras fanams per measure * O 13 40 



Cooley from thence to Tritchinopoly O 28 40 



Ditto from Tritchinopoly , 1 13 40 



Pagodas 2 10 40 



" The stone is delivered by measures, and paid for at the pollam, in the gold 

 fanam. " I am, &c. Edward Gareow." 



This letter contains very interesting topographical observations on the mine. 

 The specimens sent were of one sort, of a greyish colour, with a shade of green. 

 The entire crystals, which I selected among the broken ones, were of course few 

 in proportion ; but, with the addition of some distinct crystals, which Col. Cathcart 

 and Capt. Colin Macauley had sent me, have been sufficient to ascertain the struc- 

 ture and form of the crystals, of which an analytical description will close this 

 paper. I shall therefore now say nothing concerning their form, but proceed to 

 give an account of the varieties of corundum stone, which I have obtained from 

 India and China. 



In the year 1786, Col. Cathcart sent me a small fragment of a stratified mass 

 from Bengal, with this label ; " Corundum, much inferior in price to that of the 

 Coast.'* It is of a purplish hue ; its fracture like compact sand-stone ; and a con- 

 fused crystallization appears in all parts of the stone, by fibres of a whiter colour, 

 from which the light is reflected, as in feld-spar, &c. I have since obtained a 

 larger lump of the stone, of the same texture, but rather paler in its purplish hue. 

 Sir John Macgregor Murray informed me that it is called by the natives of Bengal, 

 corone, and used for polishing stones, and for all the purposes of emery. Its spe- 

 cific gravity is 3.876. 



Capt. Colin Macauley procured a lump of corundum from a sikuldar, (a polisher, 

 a term most appropriate to polishers of steel,) in whose family it had been above 

 20 years employed, for grinding and polishing stones or gems. The use to 

 which it had been so long devoted had occasioned grooves in its surfaces, 

 which facilitated greatly the examination of its structure. It is about 5-i- inches 

 long, 3-i- inches broad, and above 2 inches thick. On one of its broad surfaces are 

 2 oval grooves ; one of them is 4 inches long, 1 broad, and •§■ of an inch deep. 

 On the opposite side is a shorter oval groove, above 2-t- inches long, 14. inch broad, 

 and 1 inch deep. In these grooves, the ends of the laminae of the mass reflect the 

 light, like the crystals. It serves as a specimen of the simple apparatus of 

 an Indian lapidary. Stones polished in these grooves would be of the common 



* The above is the prime cost. I have been informed by correspondents, who purchased some in 

 retail, that it was sold for about 6s. a pound, at Madras.— Orig. 



