146 Washington — Submarine Eruptions of 1831 and 1891. 



Or 8-34 ) Sal ni . TTT 



Ab 28-30}- 49'43^- =1*00 • <- J ass 111, 



An 12-79 \ ^m salfemane. 



Di 17-22 i _ ._ Order 5, 



Hy 5-21 [• 29-21 



Ol _ 6-78 



L gallare. 

 K 2 + Na 2 



II 13-07 j" i0iD | CaO' " camptonase. 



Ap 5-04 5-04 J KO a x. 



Rest .... 0-91 — ^- = 0-28 Subrang 4, 

 Na O camptonose 



Mt 2-09 [ J, 49-41 -— 2 -— *— _^_ = 1.50 Ranges, 



• According to my analysis, therefore, the rock is a camptonose 

 (III. 5. 3. 4), and falls almost exactly at the center of all the 

 divisions, except that it tends to be domalkalic. As regards 

 the femic Constituents, which may be briefly considered 

 because the rock is salfemic, it falls in the dopyric section of 

 the dopolic grad, and in the premiric section of the permirlic 

 subgrad, as brought out by the following ratios : 



^ ,, P + ° o \ ' * a Di + Hy 



Grad - - = 1-93, Section of grad J ~ = 3-31. 



M Ol 



Subgrad 



(Mg, Fe)0 + CaO" 



= GO 



Na 2 0" 



(Ms Fe)0 



Section of subgrad ^-^ — — 2*35. 



to CaO" 



Mt 

 The rock is also prehemic, since -—- = 0-16, but no provision 



has been formally made for recognition of this relation in 

 rocks of the salfemane class, though the relations of Fe 2 3 and 

 Ti0 2 are expressed in the suborders of classes IY and Y.* 



According to Foerstner's analysis, as given by him, the rock 

 falls in monchiquose (III. 6. 2.4), because of the higher soda 

 and the considerable amount of lime that enters normative 

 anorthite and diopside, and thus takes up so much silica as 

 to give rise to the presence of much nephelite in the norm. 

 If, however, the alumina is corrected for two per cent of 

 P 2 5 , the subrang becomes kilauose (III. 5. 2.4), since much 

 of the lime is thus used in forming apatite, leaving more 

 silica for the soda. The relations are shown below. 



These relations, while of no importance in themselves, are 

 of interest in showing the necessity of the determination of the 

 minor constitutents for the purposes of the quantitative classi- 

 fication. The norm of III need not be considered. 



*Cf. Cross, Iddings, Pirsson, and Washington, Quant. Class, p. 134, 1903. 



