260 THE CANADIAN NATURALIST. [Vol. Yi. 



and well authenticated. Noprpjerath described augite crystals from 

 the slags of the iron furnace of Olsberg near Biggein Westphalia. 

 Montefiori Levi analysed augites taken from the slags of the iron 

 furnace at Ausjree near Lieiire. Richter described and examined 

 similar crystals from the iron works of Rufskberg in the Banat ; 

 Von Leonhard mentions acicular augite crystals in the iron fur- 

 nace slags of Skis-hytta in Sweden. F. Sandberger describes 

 similar occurences ; and numerous others might here be mentioned. 

 Mitscherlich and Berthier obtained by melting silica, lime, and 

 magnesia together, in a charcoal crucible placed in a porcelain 

 furnace, a mass possessing cleavage corresponding to the faces of 

 augite, and the hollow cavities in which were crowded with the 

 most beautiful crystals of that mineral. These are also of very 

 common occurrence in th: lava streams not only of extinct but of 

 active volcanoes ; and well-developed augite crystals have not un- 

 frequently been ejected from their craters. Olivine has been 

 observed in the slags of iron furnaces quite as frequently as augite, 

 and it, as w^U as magnetite, is one of the commonest minerals in 

 streams of basaltic lava. So is leucite, although it has not yet been 

 produced artificially. Mitscherlich observed transparent six-sided 

 tabular crystals of mica, and leaves of it several inches broad, in 

 the cavities of old copper furnace slags near Garpeiiberg in Dale- 

 carlia. Gurlt also mentions artificially formed mica, and it ap- 

 pears frequently in ancient and modern lava streams. With 

 regard to felspar, Hausmann makes mention as early as 1810, of 

 felspar crystals which had been formed in one of the Mansfield 

 furnaces. In 183J: Heme found similar crystals in the copper 

 furnace of Sangershausen after it had been blown out, and in the 

 iron furnace of Josephshiitte in the Hartz, they were also detected. 

 In 1810 the formation of felspar crystals in glass works was first 

 observed; and in 1848 Prechtl gave an account of their occurring 

 in a mass of c;lass wci^hin"; 133i- lbs. which had been melted 

 in the plate glass factory at Neuhaus. They were of various 

 sizes, some an inch in length, with perfectly sharp edges. The 

 formation of sanidine and other varieties of felspar, in lavas of 

 recent a2:e, is a matter of common occurrence. No instance is 

 known of the production of quartz from artificial silicates, nor do 

 those lavas of the present day which are highly siliceous, develope 

 it in cooling. These solidify as vitreous uncrystalline masses, but 

 many lavas of extinct volcanoes in the Andes and the Siebcnge- 

 birge contain it in well-formed crystal:*, shewing that it musthavo 

 crystallized out from the mass of the rock. 



