11-i L. V. Pirsson — Artijiclal Lava-Flow. 



which have been published in this Journal,* it lias been shown 

 so clearly that diopside and wollastonite, as produced from 

 molten solution, may contain variable amounts of lime and 

 maii'nosia metasilicates in solid st)lntion, that it would seem 

 (piitc possible that the dioi)side in the Kane glass is far from 

 being pure in composition. The analytical test proves that 

 the wollastonite is relatively a ])ure coin})oiind, and the optical 

 data, so far as they go, agree with this view. 



It is evident from the works quoted that the temperature of 

 the glass, when the wollastonite crystallized, must have been 

 lower than 1190°, since this is tlie inversion point of the 

 mineral to pseudo-wollastonite, which alone exists above that 

 temperature and up to 1512°, its melting point. The melt- 

 ing point of diopside is 1380° and the temperature of the 

 molten solution was therefore originally above this point; this 

 of course is to be expected, even though a flux is used to help 

 carry the quartz sand and lime carbonate into solution. 



Suvimary. — The study of the accidental flow of molten 

 bottle-glass at Kane, Fenn., has, brought out the following 

 chief points : 



That spherulites of varying size and character and consist- 

 ing of diopside may be formed in an anhydrous molten solu- 

 tion by rapid cooling. 



That the spherulitic type of crystallization appears to be 

 conditioned by the relation of crystal habit and properties to 

 the viscosity of the magma. The spherulites are of rapid 

 growth. 



That the brown color, which many spherulites exhibit by 

 transmitted light, is a phenomenon of light absorption. 



That obsidian may be artificially produced from a clear glass 

 and that its black color is a phenomenon of light absorption. 



That artificial wollastonite may exhibit certain characters 

 which are described. 



Sheffield Scientific School of Yale University, 

 New Haven, Conn., April, 1910. 



*Day, Shepherd and Wright, The Lime-Silica Series of Minerals, vol. xxii, 

 pp. 265-302, 1906. Allen, White and Wright, On Wollastonite and Psendo- 

 wollastonite. Polymorphic Forms of Calcium Metasilicate, vol. xxi, pp. 89- 

 108, 1906. Allen, White, Wright and Larsen, Diopside and its Relation 

 to Calcium and Magnesium Metasilicates, vol. xxvii, pp. 1-47, 1909. 



