322 



Royal Society ;-— - 



quartz. The following numbers were obtained in a determination 

 of the specific gravity : — 



Specific Gravity of Beryl A after fusion. 



No. of experi- 

 ment. 



W. 



pt. 



D. 



23376 

 2-3376 



1-3710 

 1-3699 



27-2 

 27-0 



•996603 

 •996603 



241 

 2-41 



The beryls have, therefore, lost nine per cent, of their density in 

 passing from the crystalline to the vitreous state. 



I was desirous of carefully comparing this loss of density under- 

 gone by beryls with that of rock-crystal fused under the same 

 circumstances. According to an experiment quoted by Forbes*, 

 the specific gravity of quartz of undoubted aqueous origin, and also 

 of quartz from granites, is 2'Q, and that of rock-ciystal, fused before 

 the oxyhydrogen blowpipe to an amorphous glass, 2*2. According 

 to the experiment of Le Eoyer and Dumas t, the specific gravity 

 of rock-crystal determined at 4° in vacuo was 2*652. The value 

 found by the Austrian Commission was 2*651223$. I have repeated 

 with great care the determination of the specific gravity of rock- 

 crystal, both before and after fusion, with the annexed results : — 



Specific Gravity of Rock-crystal before fusion 





JSTo. of experi- 

 ment. 



w. 



W. 



, 



i 



2-65 



I. 



1-9493 



1-2154 



o 



21 



•998047 



The above number is practically identical with those of Le Eoyer 

 and Dumas and the Austrian Commission. Rock-crystal fuses 

 very readily before the oxyhydrogen blowpipe, and, if care be taken, 

 the beads obtained are beautifully clear and free from bubbles. 



Specific Gravity of Bock-crystal after fusion. 



No. of experi- 

 ment. 



w. 



W. 



t. 



pt 



D. 



I. 



•4116 



•2240 



o 



24 



•997367 



2-19 



II. 



•4116 



•2261 



25 



•997120 



2-21 



III. 



•4116 



•2228 



24 



•997367 



217 



IV. 



•3376 



•1832 



25 



•997120 



2-18 



V. 



•1796 



•0977 



11 



•999655 



2-19 



Mean 2-19 



Rock-crystal loses, therefore, no less than seventeen per cent, of 



* Chem. Soc. Journ., new series, vol. vi. p. 225. 



t Gmelin's 'Handbook of Chemistry,' vol. iii. p. 354. 



J Ueber das Verhaltniss des Bergkrystall-Xilogranimes zum Kilogramme cler 

 K. Archive zu Paris (Wien, 1870). * I am indebted to Prof. W, H. Miller 

 for tbis reference, 



