Notices of Memoirs — Mineralogy. 135 



which I have sought to test the validity of my theory. The theory is nowhere 

 impugned by him. My "estimates" of the annual expenditure of volcanic 

 energy do not profess to greater exactness than the imperfect state of our topo- 

 graphical knowledge and the state of science will admit. They will be subject, 

 no doubt, to future correction, though I am sure without endangering the theory 

 itself which they illustrate. I cannot but remark that while Mr. Scrbpe has 

 objected to my numerical data, he has not in a single instance supplied in numbers 

 any betters ones, which, as it seems to me, every scientific objector is bound to do. 

 Mr. Scrope ends by declaring that he "prefers" his own old notions to my new 

 ones. That is natural ; but we must all yield in the end to the progress of truth, 

 and to this I am sure Mr. Scrope, whose truth love and candour I know from 

 personal intercourse, will, I hope, live to prove no exception. 



MINEEALOGY. 

 I. — MiNERALOGiCAL OBSERVATIONS ON Broohantite. Mineralogische 

 Beobachtungeu : V. Von Dr. Albreoht Schkauf. Sitzungsh. 

 d. h: ATcad. d. Wissensch. : Math.-Naturwiss. Classe. Ixvii., 

 1873. pp. 275-360. 



THIS Paper, which forms the fifth of a series of communications 

 presented by Dr. Schrauf to the Vienna Academy, is devoted, 

 for the most part, to a discussion of the crystallography of Broohan- 

 tite. Several minerals, differing from one another both chemically 

 and morphologically, have hitherto been grouped together under 

 this specific name ; and, although our knowledge of many of these 

 varieties is still imperfect, yet the author feels justified in referring 

 them to four distinct types, namely : — (1). The Brochantite of 

 Eezbanya in Hungary, of which two varieties (a and b) are re- 

 cognized ; and some of the Cornish and Russian Brochantites. (2). 

 The Waringtonite of Cornwall, and^a third variety (c) from Eezbanya. 

 (3). The Brochantite of Nischne-Tagilsk, in Siberia. (4). The Konigin 

 of Eussia, and a fourth variety (d) from Eezbanya. 



Dr. Schrauf points out the relation between the crystalline forms 

 of Brochantite and those of Malachite. Just as Malachite was 

 originally described as prismatic and subsequently determined to be 

 monoclinic, so it appears that careful measurements of Brochantite 

 tend to remove it from the prismatic system. The author believes 

 that some varieties of Brochantite are monoclinic and others triclinic. 



In addition to the crystallographic details, the paper includes a 

 comparative review of the paragenetic and chemical relations of 

 the Brochantite group of minerals. 



Two folding-plates of crystalline forms and projections accompany 

 the memoir. F. W. E. 



II. — The Fibrous Quartz of the Cape, a Pseudomorph after 

 Krokydolite. Der Faserquarz vom Cap, eine Pseudomorphose 

 nach Krokydolith. Von Herrn Dr. F. Wibel. Leonhard u. 

 Geinitz's N. Jahrb. f. Mineralogie u.s.w. 1873, Heft iv. 

 pp. 367-380. 



IT is a curious fact that whilst quartz so commonly occurs crystal- 

 lized, it has rarely been observed in distinctly fibrous forms. 



