Geology and Mineralogy. 275 



is decomposed by strong hydrochloric acid, with separation of 

 slimy silica. An analysis by Mr. R. A. A. Johnston, upon very 

 carefully prepared and apparently perfectly pure material, showed 

 it to have the following composition : — 



Silica _.. 48-96 



Alumina ..-.. __ 13*85 



Ferric oxide 25 -82 



Lime ..-- 1*17 



Magnesia 2 -65 



Potash . 3-47 



Soda 0-22 



Water (direct estimation) 3*78 



99-92 



These figures afford a ratio for RO : R 2 3 : Si0 2 : H a O closely 

 corresponding to 1:3:8:2 giving the formula H 4 (Ca,Mg,K a , 

 Na 2 ) (Fe Q Al 2 ) 3 Si.0. 10 and assuming the hydrogen to be basic, 

 the quantivalent ratio for R' : R" : Si of 3 : 9 : 16 or for bases to 

 silicon of 3 : 4 agreeing with that required for some varieties of 

 muscovite. The mineral is therefore a hydro-muscovite in which 

 a very large proportion of the alumina ordinarily present is re- 

 placed by ferric oxide, and to 'this may be ascribed its excep- 

 tional behavior before the blow-pipe; its comportment with 

 strong acids ; as likewise its noticeably high specific gravity. 



The name Baddeckite is given by the writer to this mineral 

 from the above mentioned locality where it was first found. 



5. A Text Book of Mineralogy with cm extended Treatise on 

 Crystallography and Physical Mineralogy ; by Edward S. 

 Dana. 593 pp. 8vo, with a colored plate. New York, 1898 

 (John Wiley & Sons). — A new edition of this work is announced 

 as nearly ready; the following are quotations from the Preface: 



"The remarkable advance in the science of Mineralogy, during 

 the years that have elapsed since this text-book was first issued 

 in 1877, has made it necessary, in the preparation of a new edi- 

 tion, to rewrite the whole as well as to add much new matter 

 and many new illustrations. 



The work being designed chiefly to meet the wants of class or 

 private instruction, this object has at once determined the choice 

 of topics discussed, the order and fullness of treatment and the 

 method of presentation. 



In the chapter on Crystallography, the different types of crys- 

 tal forms are described under the now accepted thirty-two groups 

 classed according to their symmetry. The names given to these 

 groups are based, so far as possible, upon the characteristic form 

 of each, and are intended also to suggest the terms formerly 

 applied in accordance with the principles of hemihedrism. The 

 order adopted is that which alone seems suited to the demands 

 of the elementary student, the special and mathematically simple 

 groups of the isometric system being described first. Especial 



