1885.] NEW YORK ACADEMY OF SCIEXCES. 59 



April 13th, 1885. 



Stated Meeting. 



Tlie President, Dr. J. S. Newberry, in the chair. 



Forty-two persons present. 



Mr. Geo. F. Kunz exhibited a Ceylonese zircon of 6^ karats 

 weight, penetrated its full length by three crystals of acicular 

 rutile, also a pearl fonnd in a common oyster, Ostrea horealis, 

 from the Shrewsbury river. This pearl bore a striking resem- 

 blance in appearance to a small hmnan eye, measuring over f 

 inch (17 mm.) across, the part representing the pupil being dark 

 green and gradually shading into pure white. It was said to be 

 the largest pearl of this variety yet observed. That portion of 

 the surface which was of a white color had the characteristic 

 wavy radiated reflection nsually observed in pearls from the 

 common conch, Stromhus gigas. Like all other pearls from the 

 common oyster it lacked the beanty and lustre requisite to a 

 commercial value. Mr. Kinz also showed a diamond of the 

 form described by him in Science of May 30, 1884, made up of 

 a multiplicity of twinnings, called also " extreme durate " by 

 the French. It had been cut into the rude outline form of a 

 brilliant, and its table had been placed on a diamond polishing 

 wheel for 100 days. The average circumference of that part of 

 the wheel on which it was placed being al)Out 2^ feet, and the 

 wheel going at the rate of 2,800 revolutions per minute, the 

 surface that traveled over the diamond table amountino- to over 

 75,000 miles. At times, four to eight pounds were added to 

 the usual two and one-quarter to two and one-half pounds of the 

 clamp or holder, and for a time forty pounds extra were added, 

 this last causing the wheel to throw out scintilations for several 

 feet. The diamond fairly ploughed the wheel, practically ruin- 

 ing it, so that it required planing before it could be further 

 used. No polish was produced, however, sufficient to give the 

 brilliancy necessary in any diamond gem. These experiments 



