256 EXPERIMENTS ON METAMORPHISM AND 



§ 2. Examination of crystals accidentally obtained in metallurgical mami- 



factures. 



It was thus that the examination of the silicates which flow in abun- 

 dance in a state of fusion from metallurgical furnaces, was naturallv 

 suggested. In accordance with the idea of Leibnitz, Professor Hauss- 

 mann, in 1816, availed himself of this kind of observation in order to 

 explain geological phenomena, and since that time, this veteran of 

 science has not ceased to render it important tributes.* Soon after 

 Mitscherlich discovered that peridot, pyroxene, and other mineral 

 species crystallize accidentally in the slags of manufactories.! It was 

 a worthy complement of his work on the relation between the forms 

 of crystals and their chemical composition, which had just made such 

 a brilliant mark in mineralogy and chemistry. Since then, under 

 this interesting point of view, metallurgical scoria has been exam- 

 ined with care by Berthier, Vivian, Bredberg, Sefstrom, Zinkeu. 

 Woehler, Karsten, Plattner, Rammelsberg, F. Sanderson, Percy, 

 Miller, and other savants. Professor de Leonhard has recently pub- 

 lished a work on this subject in which all the known facts relating to 

 it are carefully summed up and compared, t 



The products obtained in manufactories by the crytallization or 

 liquation of melted matters, are not the only ones that are of a nature 

 to interest the geologist. There are some, such as galena, oxide of 

 zin'.-, blende,* which separate themselves from furnaces either by 

 direct sublimation, or by the volitilization of a part or of the whole of 

 their elements. Among these results of condensation, the most 

 remarkable is feldspar, which has at different times been collected in 

 the upper part of the copper furnaces of Mansfield, in the sublima- 

 tions of zinc furnaces, the presence of which, simply suspected at 

 first, was proved beyond a doubt by the examinations of Heine and 

 the analysis of Karsten. § The formation of this important mineral 

 by means of vapor, merits so much the more attention, because, not- 

 withstanding many attempts, it has never yet been obtained crystal- 

 lized by a direct fusion. 



§ 3. Synthetical experiments by simple fiision or by different mixtures. 



The inspection of crystals, which are accidentally formed in manu- 

 factories, necessarily led to direct experiments in the dry way by 

 different methods. || It is to Berthier that we owe the first attempts 

 in this interesting direction. 



* Gottingsche gel. Ameigen, 1816, p. 489. — This first memoir was followed by others, both 

 numerous and important, on the same subject. 



Koch, in 1809, had desciibed some crystals of the manufactories, among others, the oxide 

 of zinc. The graphite which separates itself from cast iron had also been long remarked. 



f Ahhandlungen der k. Akademie der WissenchqfUn zur BerliTi, 1823, p. 25 — Annates de Ohimie 

 et de Physique, vol. xxiv, p. 355. 



J Dr. Gurtlt. Pyrogennete kiinstliche Mineralien, 1857. — Von Leonhard, Iluttenerzeugnisse, 

 1858. Idocrasc, gchelenite, are among the most frequent products. 



§ Poggendorff' s Aiinolen, vols xxxiii, p. 336, and vol. xxxiv, p. 531. 



II Attempts have been made to facilitate the crystallization of different substances by 

 acting upon large masses, which cool very gradually, and by blowing gas into them with 

 .a view to producing geodes. 



