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district, was the pure metal ; — he showed its different forms of 

 mass, leaf, and botrjoidal copper ; of rounded pieces, varying 

 from a rifle ball to a small shot in size, scattered through the 

 rock, called shot copjyer ; and also the metal in a crystalline form, 

 in curiously contorted spiculae, and in the thinnest laminae. 

 Associated with the metal were the various forms of granular 

 and aniygdaloidal trap, tabular spar, quartz, epidote, prehnite, 

 calc-spar, &c. ; crystals of dog-tooth spar, of calc-spar containing 

 copi)er, of quartz, &c. Some of the specimens were blackened 

 by the kiln-tires employed to facilitate the separation of the 

 matrix. The specimens were from the Minntsota, Cliff, and 

 Portage Lake districts. He also presented several specimens of 

 native silver associated with copper ; of agates from the lake 

 shore ; of chlorastrolites, found only on Isle Royale island ; of 

 sulphuret of copper and rose quartz from the noi'th shore of the 

 lake ; and of fossil corals from the drift. He thought the speci- 

 mens of value, not only mineralogically, but especially as illus- 

 trating this particular and almost unique copper deposit ; for 

 such a series he had looked in vain Avhen wishing to study this 

 subject, and he thought the present collection, with others he 

 made last winter from the same localities, would be of great 

 value to any one pursuing this study at so great a distance from 

 the copper region. 



Dr. Bacon exhibited a calculus taken from the urethra 

 of an ox. It consisted essentially of silica, with a little 

 carbonate and phosphate of lime. It measured about 

 four lines in diameter, and presented a rough or tubercu- 

 lated surface. 



Dr. Wyman asked how common calculi of this chemi- 

 cal composition are. 



Dr. Bacon said that very few cases are on record, but 

 that probably many passed unnoticed. 



Dr. Gould asked whether the lime-salts were diffused 

 throughout the mass or not. 



Dr. Bacon said that in this case they are uniformly 

 diffused. The silica was amorphous, not crystalline. 



Dr. Kneeland, who brought the specimen from the 



