460 RECORD OF SCIENCE FOR 1887 AND 1888. 



galena, aud magnetite. Of more general physical character may be 

 mentioned the work of Hcistings^ on the double refraction of calcite ; 

 remarkable as of a higher grade of accuracy than any experiments of 

 the same kind before made, and which i>rove the law of Huyghens to 

 be true to less than one part in five hundred thousand. In other words, 

 it is concluded that there is no known method by which an error in it, 

 if it is not absolutely true, can be discovered. Biickstrom- has contrib- 

 uted a paper on the thermo electricity of crystals. An excellent discus- 

 sion of the molecular structure of crystals has been given by Groth, in 

 his address before the Munich Academy. A paper read by J. W. Judd^ 

 before the Mineralogical Society of Great Britain is also an interesting 

 discussion of the development of a lamellar structure in quartz crystals 

 by mechanical means. Abstracts of a number of other papers of 1887- 

 '88 referring more or less closely to mineral physics are given in Groth's 

 Zeitschrift, vol. XV, p. 298 et seq. 



CHEMICAL MINERALOGY. 



Riggs has investigated anew the composition of tourmaline,'' and with 

 improved methods has made a series of analyses, twenty in all, of the 

 widely different varieties from typical localities. The following ratio is 

 established : Si : B : R' : O = 1 : ^ : | : 5 and the formula E9B022Si04 

 where W is the univalent equivalent of the bases with the oxygen-excess 

 incorpoi^ated in an Al=() group. If an O— H group is assnmed the for- 

 mula is written, R]nB022Si04. The typical kinds are then 



Lithia tourmaline I'^SiO;. SB.jOs 4H.2O. SAl.O;,. 2(Na,Li).30. 



Iron tourmaline l-2SiO,. 3BoO,. 4H2O3. 7A1,0-. 4FeO.Nn.2O. 



Magnesia tourmaline.. I'iSiO.. 3B3O3. 4H2O. 5A1,03. -g^MgO.fNaoO. 



WiiUing-5 has made the analyses of Riggs the basis of a series of cal- 

 culations designed to throw light upon the composition. He concludes 

 that the various varieties can be regarded as isomorphous mixtures in 

 different i)roportions of the molecules 



Sii.BfiAligNajHsOH, and SiuBcAlioMgioHcOes. 



Clarke has added some analyses^ to those i>reviously published of 

 diflerent kinds of mica, including amuscovite from North Carolina, and 

 a number of iron micas from different points. The same author has 

 studied tlie nickel ores of Oregon,'' which are similar to those of New 

 Caledonia in composition. He concludes that the parent mineral was 

 a nickel-bearing olivine. WhitfiehP contributes a series of analyses of 

 some borates, colemanite, ulexite, ludwigite,axinite, etc.,usingrecentim- 



'Amer. .Jour. Sci., 1838, vol. xxxv, 60. "'Min. petr. Mittli., 1888, vol. X, IGl. 



-(Efversigt. k. Vet. Akad. Forhaudl., '■ Amcr. Journ. Sci., vol. xxxiv, V3;\. 



No. 8, 1888. - Ibid., vol. XXXX, 483. 



•' Miu. Mag., 1888, vol. viii, 1. ^Amer. Jour. Sci., 1887, vol. xxxiv, p. "iSl. 

 ^ Amer. Journ. Sci.. 1888. vol. xxxv, 3;"). 



