12 GEGLOfilCAL MEMOIRS. 



local geological surveys, and the execution of topographico-geological 

 maps of Departments, as necessary adjuncts to the large geological 

 map of France made in 1823-40. 



M. Daubree has here published the reduced geological map of 

 the Department, and numerous diagrams, plans, and sections, with a 

 comprehensive explanatory text. This is preceded by a short Intro- 

 duction, comprising a general notice of geological phsenomena and 

 their relations. The work itself is divided into four parts. The first 

 treats of the physical constitution of the Department ; the second, 

 which is much more extensive, is devoted to the geological constitution 

 of the district, — the relative disposition of the several geological groups 

 of rocks, and the organic remains and the substances useful to man 

 that they contain. The third part comprises a classified account of 

 the minerals found in the Department. And in the fourth part the 

 author gives historical, statistical, and technical notices of the pro- 

 ducts of the mines, bogs, and quarries of the districts. 



[T. R. J.] 



On the Specific Gravity 0/ Fluor-Spar. By M. Kenngott. 



[Miner. Notitzen, Vienna, 1853, vol. ii. p. 10 et seq. Leonhard u. Bronn's N. 

 Jahrb. f. Min. u. s. w. 1854, p. 72.] 



From sixty experiments on fluor-spar, made without regard to the 

 colour of the specimens, the form of crj^stal, locality, &c., the result 

 arrived at by the author was that the mean specific gravity of fluor- 

 spar is 3-183. [T. R. J.] 



O71 Crystals o/Strontian. By A. Muller. 



[Verhandl. Nat. Gesell. Basel, 1852, vol. x. p. 103 et seq. Leonhard u. Bronn's 

 N. Jahrb. f. Min. u. s. w. 1854, p. 75.] 



The author notices some crystals of sulphate of strontian, remarkable 

 for their size and beauty, which were found in the chamber of an 

 Ammonites Bucklandi, from the Lias of the Schon-thal on the bank 

 of the Ergolz. The interior of the chamber was coated with druses 

 of calc-spar. The forms of the strontian crystals were like what very 

 commonly occur in barytes. [T. R. J.] 



Pyromeline. By Von Kobell. 



[Erdmaun's Journ. vol. Ivii. p. 44. Leonhard u. Bronn's N. Jahrb. f. Min. u. s. w. 

 1853, p. 836.] 



This is a product of decomposition ; probably of nickel-arsenic-glance. 

 It occurs as an earthy, mountain-green substance, incrusting or filling 

 small fissures in a quartzose rock, obtained in 1825 from the Frieden's 

 mine, near Lichtenberg, in Bayreuth. Pyromeline is a hydrated 

 sulphate of oxide of nickel, with some arsenious acid. The author 

 furnishes no quantitative analysis. [T. R. J.] 



