33 



A communication was received from Dr. John Locke, of 

 Cincinnati, Ohio, on his " Gravity Escapement with Detached 

 Detents," which was referred to a Committee, consisting of 

 Mr. Downes, Prof. A. D. Bache, and Mr. Saxton. 



Dr. Patterson laid before the Society specimens of two 

 minerals from the diamond mines of Brazil, received through 

 Mr. Ernest Pailhet, a merchant of Paris, now in Philadelphia, 

 by whom they were first introduced into commerce. 



One of these minerals occurs in irregular black lumps of consider- 

 able size, and is found in the diamond grounds one or two feet below 

 the surface. It is considered a certain indication of the presence of 

 diamonds, which, indeed, are sometimes found inside of its masses. 

 Its structure is perfectly vitreous, and it appears to be a pure ob- 

 sidian. 



The other, called " Diamond Carbon," or " Black Diamond," is 

 found in the same locality. It cuts all other minerals, including the 

 diamond itself, upon which it acts with as much rapidity as the dia- 

 mond dust. The specific gravity of the smaller piece is 3.01. These 

 minerals first attracted attention at the diamond mines, about six 

 years ago. The " Diamond Carbon" is sold here at 75 cents per 

 carat of 31 grains troy, being about 25 cents per grain, or about 

 six times the value of gold. 



Dr. P. conceives that the " Diamond Carbon" will be found ex- 

 ceedingly useful in the arts, being applicable to all purposes for which 

 diamond dust is now used. 



Pending nominations, Nos. 224 and 225, were read. 



Stated Meeting, September 15. 



Present, twenty members. 



Dr. Patterson, Vice-President, in the Chair. 



Lieut. J. Melville Gilliss, U.S.N., a recently elected mem- 

 ber, was presented to the presiding officer and took his seat. 



A letter was received and read: — 



From Prince Metternich, dated Vienna, February, 1847, 

 announcing a donation to the Society: — 



