I'UESIDKNT S ADDUKSS. 



The chief result of tlie experiments appears to me to be tlic 

 discovery that a melted mass which, if cooled at once, furnishes 

 a completely glassy mass, undergoes, when maintained for a 

 certain length of time at a somewhat lower temperature, such a 

 molecular re-arrangement that, on even rapid cooling, minerals 

 separate out. This is the case with all the minerals usually met 

 with in the basic rocks. When the mass has been kept in this 

 way, at a temperature slightly above the point at which the 

 glass softens, but below that at which the desired mineral 

 fuses, there may be no appearance whatever of any differentiation 

 of the parts ; but such a rapid cooling as would, before this 

 annealing process, have led simply to a glass, now gives rise to 

 a development of crystals, with glass only in the intei'stices. 



It is evident that this is parallel with the well-known 

 method of producing Keaumur's porcelain from ordinary artificial 

 glass, and with the experience of Messrs. Chance Bros., in the 

 fusion of the Eowley Bag, for casting into ornamental facings 

 for windows, doors, &c. There it was ft)und that a prolonged 

 annealing resulted in the conversion of the mass, which before 

 was perfectly glassy, into one full of minute crystals, the first 

 stage being the formation of beautifully ]Derfect spherulites. 



By this process MM. Fouque and Levy have been able 

 to reproduce both the chief types of the basic rocks — both that 

 in which the mass of the rock is made up of a great number of 

 crystals of felspar and augitc each independently crystallized, 

 and that in which the felspar crystals form a sort of 

 network, the interspaces of which are filled up wholly or 

 partially with augite, the outlines of which have therefore no 

 relation to the crystal planes of the mineral. The porphyritic 

 character is also obtained where the consolidation Las taken 

 place in two stages, the first being that in which the large 

 crystals of felspar, augite, and, where it is present, the olivine 

 have separated out, a stage which has evidently been of 

 considerable duration, and a second in which the mass, 

 prepared by the maintenance in a viscous state, was ready 

 to crystallize rapidly, though on a finer scale when erupted, and 



