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Mineralogy and Geology. 



421 



river in the province of Cohahuila. This leads me to suppose this ore 



the range of mountains running nearly north and south 



occurs m 



H. DE SEN AK MONT, 



Senarmont 



through Cohahuila and terminating about twenty-five miles north of the 

 city of Monterey.' " 



We have examined the specimens sent us by Prof. Bailey, and find 

 them to be the yellow oxyd of lead. The color is between orpiment 

 and sulphur yellow, and it glistens like a granular mica of a nearly 

 golden color. The natural surface is slightly crystalline and shining, 

 and when broken it has a scaly texture. 



5. On the Formation of Minerals; by M. 

 (Compt. Rend. Acad. Sci., Paris, June, 1849.) — Senarmont by keep- 

 ing certain solutions under pressure at a temperature somewhat eleva- 

 ted, has been enabled to form several carbonates. The material is 

 placed in a glass tube afterwards hermetically sealed, and a uniform 

 heat is sustained by putting the tube in a small chamber or oven. For 

 high temperatures the lubes were strengthened and the pressure equal- 

 ized by placing them within a gun barrel, which was half filled with 

 water and sealed up. In this way he formed — 



Carbonate of ' Magnesia from sulphate of magnesia and carbonate of 

 soda ; temperature about 160° C. It was in the state of white crystal- 

 line grains, hardly attacked by the acids. 



Carbonate of Iron from sulphate of protoxyd of iron and carbonate 

 of soda ; temperature 150° C. and above. Also, from protochlorid of 

 iron and carbonate of lime ; temperature between 130° and 200° for 

 twelve, twenty-four, and thirty-six hours. 



Carbonate of Manganese from chlorid of manganese and carbonate 

 of soda; temperature about 160° C. Also, from chlorid of manganese 

 and carbonate of lime ; temperature between 140° and 170° C. for 

 twelve to forty-eight hours. 



Carbonate of Zinc from a process like that for carbonate of iron. 

 6. On the Decomposition of Rocks ; by M. M. Ebelmen, (Ann. des 

 Mines, [4], xii, 627.)— The following are M. Ebelmen's results with a 

 trap from near St. Austle, (Cornwall.) This trap consists essentially of 

 labradorite and pyroxene. 



Alumina, . 

 Silica, 



Lime, 



Magnesia, . 

 Oxyd of iron, . 

 Oxyd of manganese, 

 Potassa, 

 Soda, 



Water, 



Trap unchanged. 



A. 



. 100 

 . 325 



. 36 

 • 17 

 . 106 



3 



33 



631 



Altered Trap. 

 B. 



100 

 212 



5 



14 



107 



2 



14 

 43 



497 



Trap more altered. 



C. 



100 

 201 



6 



12 



79 



13 

 38 



449 



Hence the trap by decomposition has lost more than a third of its 

 silica, £ of the lime, and half of the alkalies; this last shows that the 

 feldspar was the last to change and had not been wholly decomposed. 



VIII 



■Nov., 1 849. 



64 



