Wadsworth.] 414 [October 3, 



I now propose to show that in this last paper of Professor Zir- 

 kel there is the same inaccuracy of statement as existed in his 

 40th Parallel work ; and to give evidence that my main charges 

 have been well sustained by the observations of other workers in 

 the same field. 



Dr. Zirkel gives us to understand that Richthofen's classifica- 

 tion was and is generally accepted in Germany ; also, that it was 

 this classification which he (Zirkel) used in volume VI. ; that it 

 was literally the same as that published by him in 1873, and 

 which he had used in his lectures since 1863, or four years before 

 Richthofen published it. (Z. 110, 111.) If Zirkel had been pub- 

 licly teaching this classification since 1863 how could he regard 

 Richthofen's publication of it in 1867 " an extraordinary step in 

 scientific progress," as he says he did ? 



It is safe to say that principles, not names (unless they are pe- 

 culiar to the classification), are the most important points in any 

 classification. Richthofen's classification is primarily based on 

 the order of geological succession, and is restricted to the prod- 

 ucts of the massive eruptions in Tertiary and post-Tertiary 

 times, while Zirkel's classification, to which he refers, is based 

 mainly on the nature of the feldspars which the rocks contain. 

 Again the classification in volume VI. is not Richthofen's, but a 

 mongrel one ; while Zirkel's positive assertion that it is literally 

 the same as that published by him in 1873 is wrong ; for it dif- 

 fers, among other points, in the addition of the distinction of 

 younger (Tertiary and recent) and older (pre-Tertiary), as well 

 as in the insertion of several new species ; namely, augite-syenite, 

 augite-trachyte, quartz-propylite, and the corner-stone of Richtho- 

 fen's system, propylite. 



Baron Richthofen states of such classifications of eruptive rocks 

 as that upheld by Zirkel and taught by him since 1863 : — "We 

 are struck by the observation that, if they are based on any prin- 

 ciples at all, these are usually artificial. . . . Even the most re- 

 cent and elaborate systematical arrangements . . . are based on 

 almost purely artificial principles. . . . The high value of miner- 



Z. — Proceedings Boston Soc. Nat. Hist., 1882, xxn, 109-116. 

 VI. — Microscopical Petrography, or volume vi of the 40th Parallel Exploration. 

 The figures in the text after the abbreviation refer to the pages of the publication 

 mentioned. 



