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temperature conld be obtained. The authors describe four different 

 arrangements which gave a series of decreasing temperatures. 



1 st Arrangement. In this arrangement the temperature obtained was 

 very near the fusing point of platinum. Olivine, leucite and 

 anorthite could be reduced to a viscous mass which would 

 consolidate as an amorphous glass. 



2nd Arrangement. Iron and steel fused easily ; also the felspars 

 (except anorthite) and the bisilicates, augite, enstatite, &c. 



3rd Arrangement. Steel only became softened, but copper fused easily. 

 This represents the limit of fusion of labradorite and oligoclase ; 

 pyroxene and nepheline may be completely fused. 



4th Arrangement. Copper fused with difficulty. 



The materials employed in the experiments were either the chemical 

 constituents, obtained by precipitation, or the powder of the natural 

 minerals. On fusing the materials with arrangement No. 1 and allowing 

 the fused mass to cool rapidly a perfectly homogeneous glass was obtained. 

 It was found, however, that very rapid cooling was necessary to prevent the 

 crystallization of augite, enstatite, melilite and nepheline. The felspars on 

 the contrary only crystallize after prolonged cooling. These facts agree 

 with what has been stated above as to the readiness with which Fe-, Mg- 

 and Ca-silicates saturate silicate magmas. As regards the order of sepa- 

 ration of minerals in the synthetic experiments the authors state that 

 leucite, anorthite, olivine, magnetite and picotite separate out with the 

 arrangement No. 2 ; labradorite, oligoclase, augite, enstatite, hypersthene, 

 magnetite and picotite with No. 3 ; and the same minerals with nepheline, 

 melilite and melanite with arrangement No. 4, that is at a bright red heat. 

 We will now describe some of the rocks which have been synthetically 

 produced. 



(1) Oligoclase -augite rock (andesite without porphyritic crystals). 

 Obtained by fusing four parts of oligoclase with one of augite. Cooling 

 prolonged for four days with arrangement No. 3. Microlites of oligoclase 

 measuring on the average '25 mm. x '015 and twinned on the albite plan ; 

 microlites of augite of a pale yellow colour ('06 x - 02) distributed without 

 order through the mass ; also a few octahedra of magnetite developed at 

 the expense of the iron in the original augite. 



(2) Labradorite-augite rock. Obtained by fusing three parts of 

 labradorite with one of augit.e. Cooling prolonged over three days with 

 arrangement No. 8. Microlites of labradorite ('25 x '025) twinned on the 

 albite plan; microlites of yellowish brown augite ('05 x -025) possessing 

 cleavages and transverse fractures similar to those of the natural rocks ; 

 also octahedra of magnetite. 



A rock similar to the above but containing in addition a few long 

 prisms of melilite was obtained by fusing the scapolite-hornblende rock 

 from Bamle. 



(3) Olivine-basalt. Obtained from a black glass answering to the 

 composition, six of olivine, two of augite and six of labradorite. The 



