696 . NOTE ON SOME RECENT WORK ON THE ROCKS OF SAMOA. 



most frequentl}^ are of Eocene age. Those wliich are very mixed 

 sometimes antedate, and sometimes follow this geological period. 



With regard to volcanic succession, I am of the opinion that 

 in Samoa essentially the same order obtains as in the Eastern 

 Australian alkaline province, namely, the most alkaline rocks 

 antedate the more normal felspar-olivine basalts. The volcanic 

 succession so commonly observ^ed in Australian alkaline areas is, 

 however, not universal. It does not hold for the Vesuvian area, 

 nor for the Dunedin area. In mixed provinces, indeed, there 

 is seldom any regularity of succession, and this fact goes far to 

 justif}^ the genetic distinction between alkaline and calcic magmas. 



Dr. Weber's work renders it still clearer that to refer to 

 alkaline rocks as the Atlantic type, and to calcic rocks as the 

 Pacific type is an unfortunate system of nomenclature; and I feel 

 strengthened in my view that the former constitute a rift-valley 

 (katepeiric) type, whereas the latter constitute a type accompany- 

 ing mountain-folding, geanticline-formation, and overthrusfc 

 (anepeiric). 



