RICHTHOFEISPS VIEWS. 275 



from a careful study and comparison of a large number of chemical analyses 

 of crystalline rocks gathered from all parts of the world, differing widely in 

 their mineralogical development and structural habit. 



Besides these references to original contributions the reader who de- 

 sires to pursue the subject still further will find an excellent summary of 

 the views of Bunsen, Durocher, Roth, and others, published by Ferdinand 

 Zirkel in his text-book of petrography.! 



Waitershausen's Conclusion. Sartorius von Waltershauseii, after a careful 

 investigation of the lavas of Sicily and Iceland, published the results of his 

 researches in an elaborate memoir in which he presented his conceptions of 

 the physical condition of the interior of the earth. His conclusions, so far 

 as they relate directly to subjects considered here, stated briefly, were that 

 between a superficial cool crust and a solid interior there existed a broad 

 belt of fused material of undetermined thickness which furnished the source 

 of supply for the lavas poured out upon the surface. This material 

 arranged itself approximately according to its density. The most acid lava, 

 being the lightest, was situated nearest the surface, followed by that of 

 intermediate composition characterized by minerals of somewhat higher 

 specific gravity, and terminating finally with the heaviest, and consequently 

 most basic, lavas basalts carrying large amounts of magnetite and other 

 iron minerals. He concludes that in most instances the lavas were ejected 

 in the order of their position, the lightest being first thrown out, imperfect 

 separation by specific gravity being sufficient to account for all exceptional 

 occurrences. This simple and regular order of succession met nearly all 

 the requirements of Waitershausen's personal observations and were in 

 accord with his theories. 2 



Richthofen's views. Baron von Richtliofeii accepted the main conclusions 

 of Waltershausen regarding the physical conditions of the globe, agreeing 

 with him as to the evidences of a liquid mass lying between a solid 

 interior and a superficial outer crust. This liquid mass was acid 

 near the surface, basic beneath, with the intermediate transition lavas 

 between them. He traveled extensively in the volcanic regions of Europe 



1 Lehrlmch der Petrographie. Bonn, erster Band, 1866, pp. 453-473. 



'- Uebev die vulkanischen Gesteine in Sicilieu und Island und ihre submarine Umbildung, Qot- 

 tingt-n, 185i<. 



