278 Scientific Intelligence. 



take%somewhat of a yellowish tinge- Salt of phosphorus dissolves it 

 readily, with a residue of silica, to a clear glass, which upon cooling 

 becomes yellower than might be expected from the white color of the 

 mineral. With a little soda it gives a bubbly glass, dark colored exter- 

 nally ; upon the addition of more soda it gives an infusible enamel some- 

 what colored by manganese. 



Lieut. Colonel von JewreinofF has analyzed this substance with great 

 care and accuracy. The most complete analysis of three, all agree- 

 ing however closely, gave the following results. 



^ Oxygen. Oxygen. 



oilica, - . . 34-02 - . . 1766 (15) 

 Alumina, . - . 43-33 - . . 20*23 (18) 



Lim <N - - - 13-11 3-66 (16) . 



Protoxyd of iron, . . 3*02 068 (3) } 457 (4) 



Protoxyd of manganese, 1*05 023 (1) 



Water, .... 5.34 . . m '■ - 4.73 (4) 



99-87 

 Hence we deduce for the composition of this mineral, 



* ■ • * • • 



2Ca2Si+3AI2Si+4H, 

 the Ca representing or comprising the compound equivalent 



T , Mn+3Fe+16Ca. 



In accordance with this formula, the result of the analysis would be 



Silica, 



Alumina, 



Lime, 



3321 

 44 33 



1311 



Protoxyd of iron, 3-04 



Protoxyd of manganese, .... 1-13 



Wate r 



5-18 

 10000 



2. Mineralogical Notices; by Charles Upham Shepakd, M.D- 

 (Communicated for this Journal.) 



rf Lake Superior. — This singular, trap- 



-„„_...,«,„ VIV IHP nu/wi snore oj L>ake Superior. — This singular, u«»k 

 pean obsidian was presented to me by Mr. Thomas R. Dutton, on his 

 return from a tour of mining explorations on the north shore of Lake 

 superior. He informed me that it occurs in veins from one to six 

 inches wide, traversing a stratified greenstone or amygdaloid, situ- 

 ated upon Simpson's Island, as well as upon Fluor Island, which is 

 two miles west of St. Ignas. The mineral has a velvet-black color, a 

 subconchoidal fracture, and a shining vitreous lustre. Its Hardness^ 

 t>-5 . . . 7-0. Gravity er 386. It breaks with the greatest facility 



be- 

 black 



u J — —-w, •«■». UIV>UIVO Willi UIC ^ICttlV/Ofc wmm -■ — 



ing more brittle than obsidian. Before the blowpipe it fuses into a 

 glass, attracted by the magnet. 



It forms in its color and tenacity a striking contrast with the dyscla- 

 sue, a mineral found on the south side of the lake in connexion «» 

 the trap and the copper, in large sized masses of a pure snow white, or 

 pale rose color, specimens of which were two years ago presented to 

 me by P ro f. Forrest Shepherd. 



