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XX. 



ON THE FORMATION OF CRYSTALS OF CALCIUM OXIDE 

 AND MAGANESIUM OXIDE IN THE OXYHYDROGEN 

 FLAME. By J. JOLY, M.A., B.E. 



[Read April 18, 1888.] 



Lime cylinders which have been for some little time exposed 

 to the oxy-coal-gas flame, in the production of the lime-light, will 

 be found, on close examination, to exhibit a crystalline structure in 

 the neighbourhood of the flame. 



Broken up and placed under the microscope, it is seen that the 

 structure of the lime cylinder has been altered around, and to some 

 depth beneath the part played on by the flame, its amorphous 

 character being changed to crystalline : a mass, apparently, of 

 minute cubical crystals with high lustre. 



This fact having come under my observation, I thought it 

 desirable to make an experiment, using purer materials. Lime, 

 made by the calcination of marble ; oxygen and hydrogen, con- 

 taining, probably, but slight trace of impurities, were accordingly 

 employed. The lime was heaped in small broken pieces on a hearth 

 of fire-brick covered with platinum foil, and among the pieces near 

 the upper part of the heap, so as not to melt the platinum, the 

 flame was directed. In a short time it was seen that crystals in 

 aborescent forms were growing in the crevices close to the hottest 

 part of the mass. After half an hour the flame was turned off and 

 the lime allowed to cool, when it was found that very beautiful 

 crystals covered the pieces of lime near those parts which had been 

 most exposed to the flame. 



These crystals are isometric, showing the cube and octahedron, 

 the latter generally superimposed on the cube as a truncation 

 of its angles. They are limpid or subtransparent white, with very 

 high lustre, and have a plated structure on the cube faces. 1 The 



1 It is to be observed tbatfluorite bas just sucb a plated structure, and its dominant 

 c.loavage is oetabedral. 



