Journal of Applied Microscopy. 415 



Harris, H. F., M. D. Ripening Hasmatoxylin. Prof. Harris, acting upon a suggestion 

 J. R. Micr. Soc. PL 2, 236 fr. 1899. ^^^^ ^^ p^^j Mayer, has found that 



mercuric oxide (red or yellow) readily oxidizes haematoxylein into hematein. 

 He prepares the solution as follows : 



1 g. haematoxylin xtals, dissolved in lt» g. absolute alcohol. 

 20 g. ammonium or potassium alum, dissolved with heat in 200 cc. 

 distilled water. 

 Mix the two solutions at once, or better, after twenty-four hours, and add 

 one-half gram of mercuric oxide ; heat to boiling, and cool quickly. The liquid 

 may be used at once for staining. If a precipitate forms later, the solution may 

 be filtered. The addition of chloral to some of the staining fluid gave satisfac- 

 tory results. E. M. Brace. 



NOTES ON RECENT MINERALOGICAL 

 LITERATURE. 



Alfred J. Moses and Lea McI. Luquer. 



Books and reprints for review should be sent to Alfred J. Moses, Columbia University, 



New York, N. Y. 



Viola, C. Ueber Feldspathbestimmung. Zeit. The well-known method of Michel- 

 f. Kryst. 30:23-35,1898. ^^^^^ j^ ^j^j^j^ microlitic feldspar 



crystals are determined by measuring the extinction angles in easily recognized 

 zones, and ascertaining the maximum angle, is modified by Viola as follows : 



It is assumed that cross sections of a// orientations are equally likely to occur 

 in a hap-hazard rock section, and do occur, with equal frequency. 



But it is not true that all values of extinction angle between the limits of the 

 species are equally liable to occur. For example, in anorthite, in the zone 

 normal to 010, the extinction angles range from to nearly 50 degrees, but an 

 extinction of d to 5 degrees can occur through 2^ degrees, whereas an extinc- 

 tion of 40 to 4o degrees can occur through 19 degrees — that is, an extinction of 

 40 to 45 degrees is about eight times as likely to occur, in sections from the zone 

 normal to (010), as an extinction of to 5 degrees. 



The probabilities are calculated in this way for each extinction angle in 

 each zone, then the most probable and least probable angles are tabulated. A 

 number of sections in the desired zone are measured, the extinctions arranged 

 in order and compared, and the conclusion drawn. 



For example, in the zone [100] the probabilities are : 



Most Probable Extinction. Least Probable Extinction. 



*£tude sur la determination des Feldspaths dans les plaques minces. Paris, i{ 



