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used by them. They are probably prevented from taking up the 

 subject by the notion that it involves the acquisition of a fairly 

 exhaustive knowledge of that by no means easy branch of science, 

 crystallography. Dr. Rinne points out, however, that the extreme 

 refinements of determination used by the crystallographer are not 

 necessary for the purposes of the chemist, and that much simpler 

 methods are sufficient. These, and the principles underlying them, 

 form the subject of the present work. 



In the earlier sections the author deals with the geometrical 

 and optical characteristics of crystals. Then follows a description 

 of the microscope as fitted for the examination of crystalline 

 substances. The greatest amount of space is, however, devoted to 

 the methods of investigating the optical properties of crystals, 

 including a very clear account of the nature and action of polarised 

 light. In order to enable the most characteristic optical properties 

 of crystals to be readily appreciated by those wishing to acquire 

 this knowledge, the author has selected a series of fifteen sections 

 of minerals which bring out all the principal facts. A further 

 series of nine sections serve to illustrate the phenomena of circular 

 polarisation, etc. These are issued by Messrs. Voigt & Hochgesang 

 of Gottingen. ^- J- ^• 



Die Technik des modernen Mikroskopes. By Dr. W. Kaiser. 

 Second edition. 10 X 7 in. Parts I. and II., 80 pages 

 each; numerous illustrations in the text. Vienna, 1901: 

 Moritz Perles. Price per Part, 2 crowns ( = about Is. Scl). 



This work on the microscope and its manipulation is to be 

 issued in about five parts, and when complete it will undoubtedly 

 form a very useful book on the subject. In the two parts before 

 us the author deals with the optics of the microscope, the con- 

 struction of objectives and eyepieces, the mechanical arrange- 

 ments, selection and testing of a microscope, and commences to 

 give some general hints as to microscopical manipulation. The 

 special feature of the work is the large amount of attention 

 paid to the microscopes and accessories produced by the Viennese 

 firms of Pveichert, Merker, and Ebeling. It is, in fact, one of the 

 principal objects of the book to lay stress upon the progress 

 which has been made in the last twenty years in the manufacture 

 of microscopes and lenses in Austria — that is, in Vienna, for no 



