282 ‘DISCUSSION. 
FeO = 18-70% contains oxygen 4:15 
MnO = . 13 
CaO = 5:02 vs a 143 = 5-71 
MgO = 12:00 . = 4:76 = 4°76 
4°76 and 5-71 are not in the ratioof 1 to1. Here the MgO gives 
an oxygen ratio less than that of the other protoxides. 
2. Protoxides in an analysis of pyrope given in Streeter’s 
Precious Stones, 5th ed., p. 288. 
FeO = 9:5% contains oxygen 2:11 
‘56 
MnO = 2° xe ms 
(a0. = 5:0 . = 1-42 = 409 
MgO = 15-0 r os 595. = 5:96 
These figures also will not give a ratio of 1 to 1. 
3. Protoxides from an analyses of pyrope by Prof. M. Forster 
Heddle, Trans. Roy. Soc. Edinburgh, Vol. xxvmt., p- 311. 
FeO = 811% contains oxygen 1-8 
MnO = -46 : - ‘1 
CaO = 5-04 a 2 pi = ot 
gO = 17°85 ~ 108 = 708 
The figures 7-08 and 3:34 ieawies do not give a ratio of | to 1. 
4. Protoxides from an analysis of pyrope by Kobel, vide Lewis 
Abbott’s Lectures on the Science of Gems. 
= 9% contains oxygen 1:99 
OT = 3 é . bt 2 3-56 
MgO = 10 sy a PE a oi 
There is only one conclusion to be reached. If Mr. Smith’s 
standard is worth anything, Dana and Knap do not know what 
constitutes a pyrope. Dana’s Systematic Mineralogy is in its 
sixth edition, and isa standard work. Under the heading PYROPE 
Dana gives thirteen analyses. One of these shews that the ratio 
between the oxygen in the MgO, and in the other protoxides 
taken together is as 4:76 in the MgO, to 5:71 in the other pro- 
toxides together. These figures will not give a ratio of “1 to ry 
or even “at least” 1 to 1. According to Mr. Smith’s standard 
it ‘cannot be pyrope.” I must prefer to be guided by Dana. 
