258 EXPERIMENTS ON METAMORPHISM AND 



factories, that various results can be arrived at. It is thus that Gay 

 Lussac obtained peroxide of iron crystallized like natural specular 

 iron, by decomposing at a high temperature perchloride of iron by 

 means of the vapor of water. This reaction sometimes takes place, 

 as M. Mitscherlich discovered, in the pottery furnaces into which 

 chloride of sodium is thrown.* I myself tried, in 1849, a reaction 

 founded on the same principle, in order to verify, experimentally, 

 the action which, on purely geological observations, I had previously 

 attributed to veins of tin ores. By the decomposition of the bichlo- 

 rides of tin and titanium, I obtained the cr^'stallized oxide of tin, 

 having the same lustre, and hardness as the natural mineral, but 

 isomorphous, with the oxide of titanium known under the name of 

 brookite; I have also produced this last mineral itself, t By bringing 

 sulphuretted hydrogen to act on different metallic chlorides reduced 

 to a state of vapor, Durocher has obtained some of the principal 

 sulphurets contained in metallic veins, such as grey copper. | 



Instead of causing the vapors to act one on another, they can 

 be used to attack fixed substances, and thus to develope new com- 

 binations. It was upon this principle that I first artificially obtained 

 apatite, as well as topaz. § Still later I produced, by means of the 

 chlorides of silicium and of aluminium, crystallized silicates and alu- 

 minates.ll I also imitated the red oxide of manganese or hausman- 

 nite.l Mention ought also to be made here of the production of 

 dolomite by Durocher, by the action of chlorine and magnesian 

 vapors on limestone;** of the experiments of Charles Deville on 

 the alteration of silicious rocks by sulphuretted hydrogen and water ;tt 

 as well as of those of Rogers on the manner in which water charged 

 with carbonic acid decomposes, even in the cold, the principal nat- 

 utal silicates. It has been said that the vapor of water, if it is at a 

 high temperature, is sufficient to attack numerous silicates. || Thus, 

 according to M. Jeffreys, bricks heated to the temperature of the 

 fusion of cast iron give off, to a current of the vapor of water, silica, 

 which is condensed in the form of snow.§§ It is by a similar action 

 that water corrodes enamels in the porcelain furnaces. Illl 



* Poggmdorfs Annalen, vol. xv, p. 630. — M. Noggerath has also noticed it as the result of 

 a fire ia a salt mine of Wieliczka. The furnaces in which carbonate of soda is manufactured 

 at Framont in the Vosges, by decomposing the chloride of sodium by iron pyrites, have 

 produced splendid coatings of specular iron on the surface of the bricks. 



■\ Researches on the artificial production of some crystallized minerals, particularly the 

 oxides of tin and titanium, and of quartz. — (Observations sur I'origine des Jilons titaniferes des 

 Alpes ; Annales des Mines, 4th series, vol. xvi, 1849.) 



\Comptes Rendus, vol. xxxii, p. 823. 



§ Annales des Mines, 4th series, vol. xix, p. 669. 1851. 



11 Comptes Rendus, vol. xxxix, p. 135, 1854. 



^ Annales des Mines, 5th series, vol. i, 1852. 



*" Oompies Rendus, vol. xxxiii, p. 64, 1851. 



If Comptes Rendus, vol. xxxv, p. 261, 1852. 



%X Annales des Mines, 3d series, vol. vii, p. 448, 1835. 



§§ Jeffreys' s Report of the British Association, 1840. — {Bihliothique Britannique, vol. viii, 

 p. 441.) 



Ijll Alex. Brongniart and Regnault have verified this fact at Sevres. 



