and Density of Some Crystallized Silicates. 



271 



glass and that for the feldspar of the same composition is 

 considerably greater for this formula and is well beyond the 

 probable error. 



Table 5 gives the corresponding values for the calcium- 

 mao-nesium metasilicate series. Here also the law of mixtures 



Fig. 4. 



,2- 30 ' 















































































































































o 





































































Z-S5 



















' \ 



X 

























































































N 



v 











































s 















































\ 













Z-30 

































\ 



\ 











































\ 



k 











































\ 













































\ 



) 











































2:15 









































h 



CaSiOs 



20 



JO 



40 



JO 



60 



10 



80 



90 . 100 

 MgSiOs 



holds within the limits of error for the glasses, but when the 

 constant for a glass is compared with that of the crystal of the 

 same composition, the percentage of difference is as great as 

 3*2 per cent if computed from the simple formula, and 5*3 per 

 cent if computed from the n 2 formula. In this series the 

 constant for the glasses is always greater than that for the 

 crystalline material. 



The results for the CaO-MgO-Si0 2 series are listed in Table 

 6. They accord well with the former results in that both 

 constants are additive for mixtures of the glasses while neither 

 agree when minerals are compared w T ith glasses or with each 

 other. The percentage difference between the value of K 1 for 

 a glass and that of K^ for a crystalline material of the same 

 composition may be either positive or negative, and become as 



