1855.] Proceedings of the Asiatic Society. 705 



pegmatite (quartz and felspar) in which the porportion of felspar is so 

 small that for all practical purposes, it may be called a hard, fine-grained, 

 greyish white, laminated sandstone, with minute cloudy veins of titani- 

 ferous iron (perhaps Iserine or Nigrine ?) in very fine granular specks of 

 much brilliancy when seen in a bright light. The effect of these cloudy 

 veins is to give to the polished surface of the stone much the appearance 

 of a very coarse, dull, yellowish grey marble, speckled with black. 



I made the following experiments to ascertain what were its absorbent 

 and retentive properties as compared with new Chunar stone. 



For absorbence of atmospheric moisture. — A piece of Burdwan and one 

 of Chunar stone being carefully weighed and dried in a silver basin, both 

 having been previously exposed for some time to the damp air of the 

 Museum, were found to give the following results : 



Chunar stone. Burdwan stone. 



Natural weight, grs. 2204 1569 



When dried, 2198 1568 



Loss, 6 1. 



So that the Chunar stone imbibes six parts of moisture from the 

 atmosphere, while the Burdwan only takes up one part. It was found 

 after about a fortnight during the late excessively damp weather, 

 that while the Chunar stone re-absorbed something more than its former 

 weight of water, the Burdwan stone had not absorbed any ! It is 

 impossible to adduce a higher proof of the superiority of this stone in 

 this respect. 



Farther to test the stones, both were again taken in their natural state 

 and, without any drying, weighed and put into a basin where they were 

 covered with rain-water and left for forty-eight hours. At the end of 

 that time they were taken out and first gently dried by pressing them in 

 a soft cloth and then left for an hour on bibulous paper, being frequently 

 turned over so as to dry off all the loose external water. Upon weighing 

 them at the end of this time, when both were fairly saturated and free 

 from external moisture, it was found that 



The Chunar stone 2209 grs. had absorbed 34^ grs or 1.561 per cent. 



The Burdwan stone 1568 ditto 6 grs. 0.382 per cent. 



Hence if we call the result of the first experiment the chemical absorp- 

 tion it is as six to one in favour of the Burdwan stone, and if we 

 call the second experiment the mechanical absorption, this is about the 

 same, being as 0.382 to 1.561, or as four to one in favour of the Burdwan 

 stone. 



4z2 



