H. S. Washington — Rhyolites of Lipari. 459 



and basalts, inasmuch as the lavas of intermediate com- 

 position, such as those of trachytes, dacites, and andes- 

 ites, seem to be somewhat less regular, though they 

 conform in general to the same rule. This lesser regu- 

 larity may lead to the recognition of other factors in the 

 problem. 



For the sake of brevity only the figures for silica, 

 ferric oxide, ferrous oxide, and the molecular ratio 

 FeO/Fe 2 3 are given here. The complete analyses and 

 the references may be found in Professional Paper No. 

 99, except for the analyses of the Lipari rhyolites that 

 have been given in the preceding pages. The lavas of 

 the different volcanic centers are distinguished as hyaline 

 (that is, with much glass), or as crystalline (that is, with 

 no or almost no glass). A further study of these rela- 

 tions is to be made, taking into consideration many more 

 data than are given here. 



table v. 



Kelations of the Iron Oxides and Glass in Italian Lavas. 



Ehyolites. 



Lipari. 



, Hyaline > r-Crystalliiie-^ 



SiO, 74.22 73.86 71.70 74.70 69.64 



Fe 2 3 :... 0.40 0.60 0.48 1.15 1.93 



Feb 1.60 1.40 1.17 0.28 1.37 



FeO 



|^-q 7.33 4,75 5.33 0.57 1.58 



Symbol 1.4.1.3 1.4.1.3 1.4.1.3 1.4.1.3 1.4.1.3 



Sardinia. 



, — Hyaline — > r-Crystalline^ 



SiO, 74.61 70.50 73.09 72.05 



Fe 2 3 0.09 0.75 1.28 2.93 



FeO , 1.36 1.22 0.68 0.39 



FeO 



j^0 3 19.00 3.40 1.25 0.33 



Symbol 1.4.1.3 1.4.1.3 1.4.1.3 1.4.1.3 







TTv 



Pantellerites. 

 Pantelleria. 



a lin e ^ 



67.85 66.07 

 1.84 2.05 

 4.54 5.88 



5.25 6.31 

 II.4.1.3 II.4.1.3 



72.21 

 3.26 



1.07 



0.75 

 II.4.1.3 





SiO, .... 

 Fe 2 6 3 .. 

 FeO ... 

 FeO 

 Fe 2 3 • • 

 Symbol . 



. . 69.91 

 . . 1.81 

 . . 5.86 



. . 7.45 

 II.3.1.3 



69.33 

 2.65 

 5.52 



4.46 

 II.3.1.3 



-Crystalline ^ 



70.21 69.79 

 6.01 5.35 

 2.73 1.43 



1.00 0.59 

 II.3.1.3 II.4.1.3 



