KII^^G'S VIEWS. 277 



lavas, the rhyiilites, to the most basic of all, tlie basalts. From this order 

 he nowhere recognized an\- deviation. Accepting the hyi)othesis of Walter- 

 shausen as regards a li(^nid interior and the nature of the molten mass, he 

 seeks to account for the remarkable alternations observed in lavas upon the 

 surface of the globe by supposing changes to take place in the physical 

 conditions governing the emission of lavas which would from time to time 

 elevate or depress the loci of eruption. These changing conditions were 

 imiversal, producing similar resvdts in volcanic centers all over the world, 

 but not necessarily contemporaneous in time. He says: 



It appears that after the ejection of the chief bulk of andesite, when other pro- 

 cesses ending' in the opening of fraetures into the basaltic rejiion were being slowly 

 prepared in dejith, the seat of eruptive activity ascended gradually to regions at less 

 distance from tlie surface.' 



Clarence King's Views.— As a part of the report upou the Geological 

 Exploration of the Fortieth Parallel, Mr. Clarence King published in 1878 

 the results of his reseai'ches u]ion the genesis of lavas as shown bv their 

 occurrences in the field of his <)l)servations in the Grreat Basin. As regards 

 the law of succession, his views are for the most part in accord with those 

 of Richthofen, he going, however, still further and finding a nuich more 

 intricate svstem in the alternations from acid to basic rocks. He finds an 

 acid, a neutral, and a liasic member in each natural group or order which 

 he designates by specific names, each member having a definite mineral 

 composition and a fixed place in the order of succession. To these modifi- 

 cations proposed to Richthofen's order he adds another still more radical, 

 in respect to classification, uniting rhyolite and basalt under one head, to 

 which he applies a new designation, " Neolite," these two types of lava 

 constituting the acid and basic subdivisions of this natural group, having 

 the same relative ^'alue as andesite and trachyte. The sequence of lavas as 

 recognized by Mr. King is as follows :'" 



I Op clt., p. 58. 



•U. S. Gool. Explor. of the Fortieth Parallel, vol. i, Systematic Geology, \t. 690. 



