193 



Catalogue of the Books belonging to the Library Company of Phila- 

 delphia. Vol. III. Containing the Titles added from 1835 to 

 1856 : — together with an Alphabetical Index to the whole. Phila- 

 delphia, 1853. 8vo. — From the Company. 



Dr. Franklin Bache announced the decease of Dr. John G. 

 Warren, of Boston, a member of this Society, who died on the 

 4th inst. in the 7Sth year of his age. 



Messrs. Eckfeldt and Dubois exhibited to the meeting an ap- 

 paratus for ascertaining the specific gravity of ores, metals, 

 coins, gems, &c. with the following descriptive communica- 

 tion. 



The apparatus for taking specific gravity of solids is, essentially, 

 a tin cup, with a spout at the side. Five vessels are here shown, of 

 different sizes and shapes, to suit different cases. Four of these are 

 cylindrical, ranging from six to ten inches high, and from two to five 

 inches in diameter. The tall one (ten inches by two), is intended 

 for the trial of silver spoons and forks, or articles of similar shape; 

 the others are adapted to lumps of stone or metal, or blocks of wood, 

 of various sizes. The fifth vessel is rectangular, measuring 6^ inches 

 high, 1| inches long, and a inch broad, being intended for coins, not 

 smaller than the half eagle, or quarter dollar, and for small medals, 

 and gems of admissible size. This vessel is provided with a brass 

 plate, as a plunger, for diminishing the surface. The smaller vessels 

 are set firmly in mahogany blocks, to insure steadiness in the opera- 

 tion; and these blocks have screw feet, for convenience of levelling. 

 The spouts extend upward, with a curve outward, the beak being far 

 enough below the top of the cup to allow for the space to be taken up 

 by the specimen, that it may not force the water over the top nor 

 leave any point uncovered by water. The aperture of the spout is 

 tapered to the one-sixteenth of an inch, and a small bit of wire pro- 

 jects downwards from the beak, to carry the drops of water properly. 

 A small cup is placed directly under, to catch the water displaced, 

 and a brass weight, equal to the weight of this cup when empty, is 

 found convenient (though not necessary) as a counter-weight. 



When the operation is to be performed, suppose upon a gold or 

 silver ore, the ore is first weighed, and afterwards its surface is moist- 

 ened. The vessel is then nearly filled with water, and so much as is 

 superfluous, or above the level of the beak of the spout, runs or drips 

 off, to a final drop. The small cup is then set under the beak, and 



