PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 505 



times of pusliiiij; with a stick a solid lurnii of lead to the bottom of a 

 molten mass, and it would invariably rise again to tlie surface. 



The Chairniaa explained that he was present at the experiments made by 

 Professor Everett, an account of wliich was given at the time, and it was 

 found that a pig of solid lead would sink in a kettle of molten lead, but 

 whether the temperature of the molten lead was not considerably above 

 the melting point, was not carefully observed. Had the solid and the 

 molten lead been of nearly the same temperature perhaps the result would 

 have been different. 



Mr. Garvey remarked that the fact of the solid floating upon the molten 

 metal was not conclusive proof of a lower specific gravity, as there were 

 mysteries connected with the behavior of the substances under these con- 

 ditions that had not yet been unraveled. 



Dr. Parraelee observed that water, sulphur and some other substances 

 when they change from the solid to the liquid state crystalize, and the 

 crystals arrange themselves in such way as to have interstices between 

 them, in this waj' diminishing the specific gravity of the substances. But 

 substances which have not this property, increase their specific gravity in 

 passing from the solid to the liquid state. If the experiment be properly 

 and fairly tried it will be found that solid lead or iron will always sink in 

 the same metal melted. 



The Vanderbilt Medal. 



Mr. Xorman Wiard presented the designs and plaster casts of the gold 

 medal voted by Congress to Commodore Vanderbilt in recognition of his 

 munificent gift of his superb steamship, the Vanderbilt, to the nation in her 

 hour of need. The design was by Leutze and the medal is being executed 

 by Mr. Salathiel Ellis. On one side is a likeness of the Commodore in bas 

 relief, and on the other an allegorical design: a female figure representing 

 Commerce is kneeling to another, meant for America, standing upright, 

 with a huge two-handed sword on her shoulder, and with her left hand 

 resting upon a shield, while the background is filled with the spars and 

 hull of the great ship. The medal will be three inches in diameter, and 

 will cost $3,000. The ship is of 5,000 tons burden; she was built in the 

 most thorough and careful manner, and cost $800,000. 



The Chairman presented the following interesting items of scientific news: 



The Largest Diamond Known. 



This gem is in the possession of the Grand Mogul. It resembles in form 

 and size half a hen's <igQ, and weighs two hundred and ninety-seven and 

 three-sixteenths carats. It was found in the year 1552, at Colore, a short 

 distance east of Golconda, and is valued at $2,300,000. It is cut as arose 

 diamond and is perfectly limpid with the exception of a slight flaw near 

 the girdle 



Chrome Alum. 



A large quantity of chrome alum having been made at the laboratory of 

 the Glasg(>w Mechanics' Institute, the various mother liquors were boiled 

 to a syrupy consistence, placed in a bottle and laid aside. The solution 



