ACADEMY OF SCIENCES. 163 



Regular Meeting, March 20th, 1871. 

 President in the Chair. 



Donations to the Cabinet : A fine specimen of jasper, found ten 

 miles south of Merced Falls, was donated to the Society ; also speci- 

 mens of the shrub Crarrya Fremontii, gathered near the summit of 

 a mountain 4,000 feet above the level of the sea: both by Mr. J. 

 A. Johnson. 



Mr. Brooks said he had an assay made of some of the sand from 

 Black Point, but the "gold" proved to be brass. The assayer, 

 Henry G. Hanks, said he had made a careful examination 

 of the ground. On the top of the bluff, for several hundred feet, it 

 showed a dark color, and upon examination it proved to be black 

 magnetic sand. He washed sand from several parts of the ground, 

 and obtained particles of the supposed gold, pretty evenly distribut- 

 ed. When examined under the microscope the substance appeared 

 like trimmings and filings. When examined chemically, it proved 

 to be brass, as did the sample furnished by Mr. Brooks. His the- 

 ory is, that there has been a machine shop on the ground, or that 

 the brass filings have been placed there, with an intention to de- 

 ceive the public ; but it is difiicult to account for the black sand and 

 the even distribution of the brass filings. 



Mr. Durand presented a list of various minerals and mineral lo- 

 calities of the coast, Avhich have not before been made public. 



Professor Davidson reported that the apparatus he had devised 

 for recording sub-surface temperature for great depths, by means of 

 an electro-thermal pile, had made good progress, even against the pre- 

 vious opinions of the instrument maker himself. It is proposed to 

 register the depth by the well-known means of breaking the circuit 

 of an electrical current passing through two insulated wires in the 

 sounding line — say every 100 fathoms — by means of the wheel- work 

 of W^assey, or similar apparatus. In the changes of temperature, 

 an electro-thermal pile eighteen inches long, insulated, surrounded by 

 a non-conductor except one end, is used in combination with a Thomp- 

 son's Reflecting Galvanometer, not hable to derangement on ship- 

 board. At every 100 fathoms, when the chronograph registers the 





