J. P. Cooke, Jr., on Atomic Ratio. 387 
atomic ratio of garnet is 6:6:12 or 1:1:2. So in like man- 
ner the ratio for orthoclase is 2:6:24 or 1:3:12. On the 
other hand from the ratio we can as easily construct the symbol. 
For example the ratio in the case of anorthite is 1:3: By 
doubling this, (2: 6:8) we make the first term divisible by 2, 
the second by 6, and the third by 4 the quantivalences of the 
several radicals associated in the mineral. Thus we have the 
ii vi iy 
skeleton as it were of the mineral R, [R,], Si, and we now 
easily add the number of oxygen atoms required to “close” 
the molecular group, which gives us for the full symbol R, 
[R, ]*iiO , viiiSi,. In like manner from the ratio 1:3: 6 we first 
ii 
deduce the number of atoms of the three radicals, namely R, 
[R,], Si, and then we add, besides the eight atoms of oxygen 
required to unite the basic radicals to the atoms of silicon, also 
tal sums thus obtained. For example Moberg’s analysis of the = 
Bohemian pyrope gave the following results. 
Si 1930 or SiO, 41°35 
[Al] 11°92 Al,O; 22°35 
Fe 7°73 FeO 9°94 
Mn 2°01 MnO 2°59 
Mg 9°00 MgO 15°00 
Ca (377 CaO 5°29 
Cr 8-19 C 4°17 
O 43°17 
100°69 100°69 
Dividing now each per cent by the atomic weight of the 
tadical and multiplying by its quantivalence we obtain the fol- 
, numbers : 
Si (18-30 +28) X4=276 276 
[Al] 11°92 +- 54.8)X6=131 131 
F 745 56° KX SS Vs 
Mn 90] = 55 xX 2=> 007 ' 
Mg Fiend ae NK 2 OS 
Ca $77 = 40 = X 2 = 0°10 
Cr $19 = 522)x2=—012 140 
