8 PROCEEDINGS OF THE CALIFORNIA 



Dr. Cooper remarked that, since the publication of his paper on 

 Californian Mollusca, read before the Academy November 3d, 1862, 

 (see Proceedings, vol. II, p. 202) he finds the generic name 

 Strategus preoccupied, and he now proposes, in its place, the 

 name Navarchus. 



Professor Whitney exhibited a magnificent specimen of auriferous 

 quartz, in which the gold was associated with Mispickel, (Arsenical 

 Pyrites.) The weight of the mass was about five pounds, and the 

 value of the gold estimated at $1,500. It was obtained from the 

 celebrated " Fellows Lode," on the Middle Yuba, in Sierra County. 

 It is stated, on what is believed to be reliable authority, that from 

 $200,000 to $250,000 has been taken from an excavation on the 

 lode only ten feet long and four feet wide, by crushing in hand- 

 mortars. The occurrence of gold in connection with mispickel, in 

 the California mines, seems to be rare, at least in the southern 

 counties. In the specimen presented, the gold formed a coherent, 

 sponge-like mass, when the mispickel was dissolved. 



Baron Richthofen remarked, that gold occurs associated with 

 mispickel in Silesia. 



Mr. R. L. Harris made some remarks on the comparative fric- 

 tion of car-wheels, on an iron track, when rolling and sliding, as 

 shown by experiments made on the street-railroad in Washington 

 street. Here the greatest grade is five hundred and twenty-eight 

 feet per mile, or one in ten, and it is found that, on a wet day, if 

 the wheels are stopped by the brakes, they will slide on the track ; 

 while, if the brakes are not put down so hard but that the wheels 

 can revolve, the car is entirely under control. This is not the 

 popular opinion, and the authorities generally state, that the slid- 

 ing friction is the greatest ; but experience shows, that the fric- 

 tion is really greatest when the sliding and rolling motions are 

 combined. 



