268 E. 8. Larsen — Relation between the Refractive Index 



Table II. 



Per cent 

 CaSi0 3 



d 



w. 



60 



N u 



N Na 



N T h 



3 

 l_ 



o 

 o 



T-l 



% 



D 



> 

 II 



th|P 



o 

 o 



TH 



1 > 

 > 



100-00 



o-oo 



1-6242 + 

 1-6240 + 



1-6281- 



1-6280 



1-6317 

 1-6317 



•0075 

 •0077 



o-oo 



2-904 

 2-904 



•3444 



o-oo 



95-00 



5-00 



1-6224 + 

 1-6221 



1-6263 + 

 1-6260 + 



1-6300 

 1-6299 



•0076 



•0078 



+ 0-04 



2-899 



•3450 



-0-09 



85-26 



14-74 



1-6183 

 1-6187 



1-6222 

 1-6225 



1-6256 

 1-6260 



•0073 

 •0073 



+ 0-09 



2-892 

 2-891 



•3458 



-0-34 



74-00 



26 ; 00 



1-6135 

 1-6136 



1-6175 

 1-6174 



1-6210 

 1-6210 



•0075 

 •0074 



+ 0-13 



2-882 

 2-880 



•3471 



-0-57 



64-00 

 60-00 



36-00 

 40-00 



1-6084 

 1-6084 + 



1-6068 

 1-6067 



1-6122- 

 1-6122 + 



1-6106 

 1-6104 



1-6155 + 

 1-6156 + 



1-6140 

 1-6139 



•0071 

 •0072 



•0072 

 •0072 



+ 0-09 

 + 0-11 



2-872 

 2-873 

 2-870 

 2-858 



•3482 

 •3499 



-0-80 

 -0-51 



53-64 



46-36 



1-6038 

 1-6035 



1-6074 

 1-6072 



1-6111 



1-6107 



•0073 



•0072 



+ 0-10 



2-854 

 2-854 



•3504 



-0-71 



40-00 



60-00 



1-5970 

 1-5971 



1-6006- 

 1-6008 + 



1-6035 + 

 1-6040 



•0065 

 •0069 



+ 0-09 



2-835 

 2-834 



•3528 



-0-73 



30-00 

 10-00* 



70-00 

 90-00* 



1-5926- 

 1-5921 



1-5819 



1-5818 



1-5816 

 1-5814 



1-5963 + 

 1-5957 



1-5856- 

 1-5854 



1-5851 

 1-5850 



1-5994 

 1-5990 



1-5887 

 1-5887 



1-5883 

 1-5880 



•0068 

 •0069 



•0068 

 •0069 



•0067 

 •0066 



+ 0-09 

 + 0-03 



2-819 



2-823 



2-820 

 2-881 

 2-877 

 2-879 

 2-880 

 2-879 



•3545 

 •3599 



-0-76 

 -0-28 



5-00 



95-00 



1-5787 + 

 1-5789 



1-5820 + 

 1-5823 



1-5854 



1 -5854 



•0067 

 •0065 



-o-oi 



'2-777 

 2-777 



•3601 



-0-45 



o-oo 



100-00 



1-5768 

 1-5766 



1-5802 

 1-5800 



1-5835 

 1-5831 



•0067 

 •0065 



o-oo 



2-758 



2-757 



•3627 



o-oo 



* These two determinations were made on glasses from separate melts. 



additive value. For the (Ca,Mg)8i0 3 series the values are 

 negative and show clearly a contraction on mixing. The data 

 for the feldspar glasses are not consistent. 



The data for the refractive index and density of the various 

 crystalline forms were taken from measurements made in the 

 Geophysical Laboratory on pure artificial material. The prob- 

 able error of the index of refraction is about ± 0*002, while 

 that for the density is about ± 0*005. The indices of refraction 

 of quartz and of the feldspars are those of the natural minerals. 



