CLASSIFICATION OF IGNEOUS ROCKS 267 



If the ratio of the total weight of the salic minerals to that 

 of the femic minerals be greater than 7 to 1, the rock falls 

 within the persalane class ; if it fall short of this, but is more 

 than 5 to 3, it is in the class of the dosalanes. If the ratio 

 lie between f and §, the rock is a salfemane, if between f and y r 

 a dofemane ; and if less than y, a perfemane. 



(4) The Orders 



Each of these five classes 1 is again divided into orders. The 

 subdivision into orders of the first three classes — the persalanes, 

 dosalanes, and salfemanes — depends on the proportion of felspars 

 to quartz on the one hand and felspathoids on the other. As 

 is well known, these do not occur together. There are nine 

 orders in each class, as shown by the following table, where Q 

 denotes quartz, F felspar, and L lenad or felspathoid. 



1. ^-> ^-perquaric. a ^L<—> — quardofelic. 7 — - <-^-> -2-lenfelic. 

 Fi rn ^ F s 7 ' F 3 5 



2. -^-<— >— doquaric. c -±-^ — < — perfelic. 8.^=, <— >— dolenic. 

 F i 3 J F 7 F i 3 



7. ^<- 5 -> — quarfelic. 6. -^ <— > — lendofelic. n — > i— perlenic. 

 ^ F 3 5 F57 * F 1 r 



The dofemane and perfemane classes are each divided into 

 orders - according to the proportions of femic silicates to non- 

 silicates. 



Most of the orders have received special names ending in 

 " are," and based on the names of countries or of states. For 

 instance, the quardofelic order of the persalanes is known as 

 Britannare, the perfelic order of the dosalanes as Germanare. 3 



(5) The Rangs and Snb-rangs 



Each of the orders of the first three classes is subdivided 

 into five minor groups, known as " rangs," according to the 



1 There are also sub-classes, which are only of importance in the case of rocks 

 with a considerable amount of corundum (see post, p. 271) and zircon (in the first 

 three classes), or apatite, fluor, etc. (in the last two). 



2 These are again split up into sections of orders according to the ratio of the 

 more acid to the less acid femic silicates, or into sub-orders according to the ratio of 

 the iron ores to the titanium minerals. 



3 The sections of orders and sub-orders have similar names, the former ending 

 in -iare, the latter in -ore. 



