and Laboratory Methods. 1433 



2 V,^ from a ft y 

 31°48f 

 31 111 

 30 38| 



The pleochroism was : 



For vibration parallel c(=r) deep blue with feebly violet tone. 

 " " " a(=/' ) pale yellow to brownish yellow. 



" " " b(=<!') feeble green to gray green. 



The transparent blue spinel of Ceylon was also examined optically and as to 

 form. A. J. M. 



vonWorobleff, V. Krystallographische Studien ^f^g^ ^ historical review with bibliog- 

 iiber Turmahn von Ceylon una einigen ° 



anderen Vorkommen. Zeit. f. Kryst. U : raphy the author proceeds to a careful 

 263-454, 1900. examination of some hundreds of fine 



crystals obtained by Dr. Griinling in Ceylon, and now in the Berlin museum, and 

 also others from other museums. The entire recorded series of forms are com- 

 pared and tabulated by zones, and with respect to antilogous and analagous 

 poles. One hundred and thirty-one new forms are recorded, and a discussion of 

 the relation between crystal form and pyro-electrical behavior of tourmaline in 

 general is given, and finally the conclusion is reached that the mineral belongs 

 to the ditrigonal-pyramidal class of symmetry. a. j. m. 



Ooldschmidt, v., and Preiswerk, H. Chryso- Good illustrations of two-circle measure- 

 beryllzwilling von Ceylon. Zeit. f. Kryst. i , . 



iZ: 455-467, 1900. ment and calculation. 



Goldschmidt, V. Zur Theorie der Zwillings-und 

 Viellingsbildungen. Zeit. f. Kryst. li : 

 468-476, 1900. 



Smith, G. F. H. A Three-Circle Goniometer. ^^e object of goniometrical measure- 

 Min. Mag. 12: 175, 1899. ■" ^ 



ment is to determine in the simplest 



and quickest manner the geometrical constants of crystals, and the indices of 



their faces. The relative advantages and disadvantages of the one- and fev^-circle 



goniometers are pointed out, and the author states that the advantages of both 



instruments may be combined by the addition of a third circle. A detailed 



description of the instrument is given (with plate) and the method of use 



described, some actual readings being recorded. l. mci. l. 



Smith, 0. P. H. Note on the Identity of Para The oxychloride of lead rafaelite 



laurioniteand Rafaelite. Min. Mag. 12 : 183, ., -u 1 u a -n j i. u 



jg ** -^ (described by Arzruni) proved to be 



identical with paralaurionite by com- 

 parison of angles, made by twinning and optical characters, the only difference 

 being in the color, P. being white while R. is violet-red, and shows strong pleo- 

 chroism. Axial ratio of Y.^=a : b : r=2.7036 : 1 : 1.8019. l. mci. l. 



