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Mineralogy and Geology. 273 



I have already in a previous note indicated tlie manner In which I sup- 

 pose these silicious and argillaceous magnesites and doloraites to have 

 been in certain parts of the formation transformed by the intervention of 

 solutions of alkaline carbonates into silicates, such as talcj serpentine, 

 chlorite, pyroxenite, etc. A farther development of my views of the 

 metamorphism of sediments, with the results of the investigation of a 

 great many altered rocks will appear in the Report of Progress of the 

 Geological Survey of Canada for the last three years — now in press. 



Montreal, July 6th, 1857. 



2. Chlorids, — At the recent eruption of Vesuvius (in 1855) Deville made 

 some observations on the material issuing from fumaroles over the cooling 

 lava, and found that there was no vapor of water, and that the chlorids 

 of sodium and potassium predominated, while there were sulphates in 

 small quantities, no fl.uorids, and perhaps some carbonic acid. The un- 

 condensable gases he has not yet satisfactorily examined. Higher above 

 where the heat is less, the smell of sulphurous acid was perceived, but 

 the fumaroles still gave out almost exclupively chlorid gases. In places 

 where the vapor of water was given out, as in the upper crater, sul- 

 phurous acid w^as more abundant and the odor of sulphuretted hydrogen 

 was perceptible with perhaps vapor of sulphur; from a fumarole a con- 

 siderable amount of water was condensed, upon which small crystals of 

 sulphur floated. It appears therefore, that at the points of maximum 



I intensity in an eruption, chlorids are given out without water; but in the 



places where the action is of the ordinary kind about the summit, sulphur 

 and vapor of water are abundant. 



3. Agalmatolite ; by Dr. C. T. Jackson, (Proc Bost, Soc. Nat. Hist., 

 \i, 52.) — To this mineral is referred a rock with a soapy feel from the 

 borders of the Deep River coal field. North Carolina. It afforded Dn 

 Jackson on analysis. Si 75*00, *1 IS'tS, fc 2-00, fl: 3-50 = 99*25 with traces 

 only of oxyd of iron. It is ground up and sold in New York at |40 a ton, 

 making a delicate wdiite substance satin-like in feel similar to China clay. 

 It is supposed to be used in adulterating white lead and also fancy soaps, 

 and for glazing or satinizing wall-paper. 



4. Corundum. — Artificial crystals of sapphire have recently been 

 obtained by using an ordinary crucible in a forge, by A. Gaudin (LTn- 

 stitut, No. 1214). He mixed, in the crucible, lampblack, ammonia or 

 potash alum previously calcined with an equal weight of sulphate of pot- 

 ash, and subjected the whole to a high heat for 15 minutes. He thus 

 obtained the alumina crystallized without discoloration from a trace of 

 iron or any other metal The sulphuret of potassium produced through 

 the reaction is reo-arded as an energetic solvent of the alumina, and from 

 it the crystallizatfon takes place, either through its evaporation or greater 



-- .^.^.^ .^^k of Hungary. — A slate resembling talcose slate, from the 

 Gabbro or Zipser in Hunn-ary, and also much like the Sericite slate of 

 Taurus contains, according to C. F. Chandler, (Inaug. Dissert.): 



Si 3tl Pe % ^^a fi: fl 



T5-28 1343 1-88 1*79 OS? 454 2-49— 99-78, 



Specific gravity 2 '65 9. 



SECOND SERIES, VOL. XXI\r, NO. 71. — SEPT., 1857. 



35 





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concentration. 



