54 Miscellaneous. [jan. 



Submitted, an essay on the land and fresh water shells of India, hy Lieute- 

 nant T. Hutton, accompanied with specimens of the same. 

 [This will be published in our next.] 



Submitted, a note by Lieutenant Colonel Hodgson on the use of glass for 

 the balance wheels of chronometers, accompanying a pamphlet on the sub- 

 ject, by Arnold and Dent, presented by the same member. 



XIII . — Miscellaneous. 

 1. — Correction of an Error in Gregory's Mathematics. 

 As Gregory's Mathematics is generally used as a book of reference you would be 

 the means of saving many from error by correcting in the Journal of Asiatic 

 Society, the following misprint at page 297. T. 



307 v^R-A) 

 For V = .^/(R—^). 



si— iiog.(s+H) 



307 (t/R-rfc) 



Read V = T | (v/ R— t'o). 



Si— i log. (S-H$) 



2. — Tufa Formations in Persia. 

 Having procured a party of horsemen, we proceeded over some very rugged 

 ground, five miles in unE. S. E. direction, when we came to the ruins of the palace 

 erected by Suliman, one of the first khalifs of Bagdad. It is a fine quadrangular 

 structure, built round a natural basin of 70 yards in diameter, and presenting one 

 of the most singular phenomena in nature. A small channel, of four inches wide 

 and three deep, carries off the superfluous water, which appears to be considerably 

 agitated by a strong spring ; on a nearer approach this is found to be occasioned 

 like the smaller one of Yakout Buttak, by gas, which is only confined by the body 

 of water through which it forces its way. The water flowing from this fine 

 reservoir forms small pools outside the gates, and a deposit of tufa immediately 

 takes place, of which the whole hill is composed, and has most probably been 

 formed in a similar manner, though it has now reached a height of 300 feet. The 

 water appears to occupy a greater space below than above, but all the line I 

 could procure (400 feet) was insufficient to find a bottom, either at the side or 

 centre, where I was able to go on a raft. The whole of the mountains about 

 appear to be of a similar formation, and the brooks are almost filled up by large 

 masses of light porous tufa. Madrepore is also abundant. The place is highly or- 

 namented in the arabesque manner, and has been one of the best modern buildings 

 in Persia. To the north, on the top of one of the highest peaks of Balkas, stands a 

 strong castle, with four towers, and about 100 yards of a side. I could not ascertain 

 to what era it belonged, but imagine it was far anterior to Muhammedanism, and 

 probably was a fire temple of the later period. It had no Arabic inscriptions, 

 which every where cover the walls of the lower building. After a minute survey 

 of the palace, and getting some of the Arabic inscriptions copied, which were only 

 verses from the Koran, or moral sentences, I proceeded to a remarkable peaked 

 hill, about two miles to the south-west, called the zendan, or prison. With con- 



