1882.] 115 fZirkel. 



ordinary reader of my report, and I believe, that my text is 

 guilty of no inconsistency whatever. 



13. Mr. Wadsworth's phrase, " the quartz found in the rhyo- 

 litic groundmass is regarded by me as a devitrification-product," 

 (b. 269) is unintelligible ; if he means by the expression devitrifi- 

 cation product a product of the solidification of a molten mass, Mr. 

 Wadsworth's opinion is commonly shared by lithologists the world 

 over. If, however, he regards this quartz as a product of the 

 alteration of an originally glassy rock, how are its abundant 

 hexagonal glass inclusions to be explained? 



14. Mr. Wadsworth opposes the separation of the andesites 

 into hornblende- and augite-andesites (b. 265). It seems such 

 a hopeless task to endeavor to explain to one holding the 

 extreme views of Mr. Wadsworth the reasons why all pedog- 

 raph ers of the world maintain such a distinction, that it may not 

 appear unreasonable if that question be set aside peremptorily. 



15. The members of a series of trachytes (b. 266) are held by 

 Mr. Wadsworth to be basalts. This seems to render it proper to 

 instruct him, that a rock in which sanidine prevails and which 

 does not contain olivine never can be named a basalt. 



16. Mr. Wadsworth asks naively, how the absence of olivine 

 absolutely separates a rock from the basalts (b. 267). It might 

 be replied, that the absence of olivine separates a rock from the 

 basalts just as the absence of quartz separates a rock from the 

 granites. 



17. In referring to the rocks in which I have sought to 

 demonstrate the presence of nepheline, Mr. Wadsworth allows 

 himself to distort my words in a very bold and unjustifiable man- 

 ner. In the case of one rock which does not contain olivine, I 

 have concluded from its gelatinization that the colorless ingre- 

 dient, which resembles nepheline, is nepheline. In the case 

 of another rock, which does contain olivine besides the same 

 colorless mineral, I have supposed the latter to be nepheline 

 again from the fact that the rock gelatinizes much more stro?igly 

 than it would, were only olivine present. I should not be likely 

 to take for granted the presence of nepheline simply from the fact 

 that a rock gelatinizes. 



