250 MINERALOGY. 



ing another subsystem, to be called the cUndhexagonal. In all these 

 sections the angles of the axes will be ^=^=90°, ry^ 90° \i.e. two 

 axes at right angles, and the third not] ; and the parametric ratios in 

 the general case are h:a: c =m : 1 : n ; but in the clinohexagonal 

 subsystem h-. a i g= i^^ '. 1 \n [similar to SchrauFs orthohexagonal 

 system, where a '.h=z isj^ : 1\ while in the clinoquadratic subsystem 

 6 : a : c=l : 1 : n [i.e. two axes equal, the third not]. F. W. B. 



ScHRAirp, Prof. A., and E. S. Dana. Notiz iiber die thermelektrischen 

 Eigenschaften von Mineralvarietaten. [Thermo-electric properties 

 of Mineral varieties.] Sitzungsb. k.-k. Ak. "VViss. math.-nat. Classe, 

 Abth. 1, Bd. Ixix. Heft 3, pp. 142-159, with a woodcut. Trans- 

 lated in Amer. Journ. ser. 3, vol. viii. pp. 255-267. 

 The results of many experiments are set down in tables, from which 

 the following general results are to be gathered : — In the combination 

 of sulphur with the negative metals Bi, Co, Ni, Pb, the character of 

 these overcomes the influence of sulphur: a mixture of antimony 

 weakens this negative character, but tellurium strengthens it. Among 

 the combinations of iron the arsenides are negative, but most of the 

 sulphides are positive. The authors have increased the number of 

 minerals which vary in being sometimes positive, sometimes negative, 

 by four species, viz. Tetradymite, Glaucodote, Skutterudite, and Arse- 

 nical pyrites. The change of signs in these cases can have nothing to 

 do with right or left hemihedral crystallizations ; and the cause is 

 therefore supposed to be in all cases chemical composition ; in the 

 first three and some others the sp. gravity of the positive variety is 

 less than that of the negative. E. B. T. 



ScHEODER, Dr. H. Untersuchungen uber die Yolumconstitution 



, einiger Mineralien. N. Jahrb. Heft iv. pp. 399-402, pp. 413, 



414 ; Heft v. pp. 506-513 ; Heft vi. pp. 600-605 ; Heft vii. pp. 



711-714 ; Heft viii. pp. 805-816; Heft ix. pp. 943-952. 



Continuation of the author's researches on the volume-constitution 



of certain minerals. 



Senft, Dr. Analytische TabeHen zur Bestimmung der Classen, 

 Ordnungen, Gruppen, Sippen, und Ai-ten der Mineralien und 

 Gebirgsarten. [Tables for determination of minerals and rocks.] 

 Pp. 102. 8vo. Hanover. 



SIE^VERT, Dr. Max. Ueber den Manganapatit und die Zusammenset- 



zung des Apatits. Zeitsch. gesam. Nat. vol. x. n. ser. pp. 339- 



349. 



Describes a mineral found at San Eoque, near Cordoba, where it is 



associated with beryl. The new mineral was at first taken for chiyso- 



beryl ; but its analysis has shown that it is a variety of apatite, in which 



part of the lime is replaced by protoxide of manganese ; the author 



therefore proposes to distinguish it as Mangan-apatite. [The formulae 



given are evidently misprinted.] F. W. R. 



