130 Prof. Mitscherlich on the Production of 



toxide of iron and lime, of lime and magnesia, which are 

 formed among the slags of iron furnaces ; these possess the 

 same primitive and secondary forms as pyroxene. I possess 

 also the trisilicate of lime, the protoxide of copper, the oxide 

 of zinc, the deutoxide of copper, the magnetic iron^ore (pxU 

 dumferrosoferricum,) the sulphurets of iron, zinc, and lead ; 

 the arseniuret of nickel, &c. 



1. Having the form of Peridot.— /The silicate of iron is 

 an important compound in the processes of melting copper 

 and iron. I found two varieties, 1. from the melting of 

 copper, and 2. from the refining process of cast-iron, com-, 

 posed of 



Silica, . , 30.93 81.06 



Protoxide of iron, 69.07 67.34 



Magnesia, . . 0.00 00.65 



100.00 99.05 



Another variety formed in a high furnace, yielded to me as 

 much as 12 p. cent, carbonate of lime; the oxygen of the silica, 

 however, was the same as that of lime and protoxide of iron 

 taken together. All these crystals have exactly the same 

 form as peridot, whose primitive form is a right rectangular 

 prism, and which, therefore, is the form of those silicates, 

 whose bases have two atoms of oxygen. The common varie^ 

 ties resemble Fig. 33. of Plate III ; and Fig. 34. is the projec- 

 tion upon the plane of P, of all those secondary faces which X 

 have observed in any of those slags, in Peridot, and in Hya- 

 losiderite together. The latter has been described by M. 

 Walchner ; it is a Peridot, which contains more iron than the 

 common varieties. 



2. Having the form qf Pyroxene.— When I came to Paris, 

 M. Berthier had the kindness to communicate to me the re- 

 sults of a vast number of researches, which he had instituted 

 on the fusibility of the silicates. Some of these silicates had 

 crystallized and assumed the crystalline forms, the same 

 angles, and the same essential external characiers as those 

 minerals which possess, a similar mixture. Thus M. Ber- 

 thier has fused siiica, magnesia, and lime, in a carbon crucible 

 in the necessary proportions to form a bisilicate, in which the- 



