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the lump is carefully lowered into the vessel by a hair wire, or waxed 

 thread. This, of course, displaces its own bulk of water, which runs 

 off into the small cup, gradually coming back to the former level, by 

 a final drop. The weight of this water is the divisor, the weight of 

 the lump the dividend, and the quotient is the specific gravity. 



In connection with this apparatus, the following miscellaneous re- 

 marks are offered to the Society. 



The opening of the gold mines of California brought out a great 

 number of beautiful specimens of gold in the matrix (or mingled with 

 quartzj of the most fanciful forms, and every variety of size and va- 

 lue. In many cases it was presumed, by the holders of these prizes, 

 that they would bring more money, as curiosities, than as bullion; 

 and, at any rate, very many owners were unwilling to have such 

 attractive specimens spoiled until they had been sufficiently exhibited. 

 At the same time, it was always desirable to know, pretty nearly, how 

 much gold was actually contained; and, to obtain such estimates, 

 upon what was supposed to be reliable authority, many of these spe- 

 cimens were brought to the assay office of the mint. They came at 

 a time when we were overpowered with the legitimate business of the 

 office, and yet it seemed impossible to refuse such requests; and, for 

 a considerable time, such employment was interesting as a matter of 

 scientific inquiry. Especially when we could compare our estimates 

 with the more definite and accurate results obtained by putting the 

 specimens or "nuggets" through the regular routine of melting and 

 assay. On one occasion a lump, weighing over 200 pounds, came to 

 us for this purpose. It was sent by the Isthmus route, at a time 

 when transportation was enormously dear, and having visible gold on 

 the surface, was expected to be rich throughout the mass; and, with 

 this expectation, was on the way to London, to make an impression 

 upon the stock market there. By the aids of a very large steelyard 

 beam and copper kettle, we were enabled to take the specific gravity, 

 but could not make it higher than that of compact quartz. The result 

 seemed so questionable, that we obtained permission to break up the 

 rock, and found that what little gold it contained was at the surface. 



Not only were ores brought to us from California, to be estimated, 

 but also from other mining regions, and of various metals; but chiefly 

 gold and silver. As the specimens were of all sizes, these demands 

 upon us often proved embarrassing, since it was necessary to have 

 beams suited to them, and with attachments for weighing in water. 

 We therefore had frequent recourse to the method advised by the el- 

 der Dr. Patterson (formerly President of this Society), which con- 



