894 SEC. 17. MINERALOGY, CRYSTALLOGRAPHY, ETC. 



3475. Plate of Bock Salt, 60x60 mm. 



W. 8teeg, Hamburg vor der Hohe. 



3476. Calcspar Rhomb oh edr on, with glasses ground parallel 

 and perpendicular to the axis. Wilhelm Steeg, Hamburg. 



3477. Calcspar Prism, with plane parallel to the axis. 



Wilhelm Stceg, Hamburg. 



3478. Piece of Sulphur with large Crystals. 



Prof. A. Mitscherlich, Miinden, Hanover. 



E. Mitscherlich by these crystals of sulphur determined the crystalline form 

 of the sulphur from the molten condition, and discovered the dimorphism of 

 sulphur. 



b. MODELS AND DIAGRAMS OP CRYSTALS, ROCKS, MINERALS, &c. 



3479. Diagrams and Microscopic Slides, demonstrat- 

 ing the structure of Bohemian Basalt. 



1. Diagram representing the most important types of Bohemian 

 Basalt. On six plates. 



2. Diagram showing the most important types of Phonolite, 

 Trachybasalt, Trachylitbasalt, and Melaphyr rocks. On four plates. 



3. Two boxes containing 10 microscopical preparations of the 

 above-mentioned rocks. 



4. Professor Boricky's works on the Basaltic and Phonolithic 

 rocks of Bohemia, with short explanation of the Melaphyr 

 illustrations. Dr. Emanuel Borricky, Prague. 



3480. Photograph of the Hitter sgriin Meteorite. 



Royal Mining Academy, Freiberg, Saxony. 



3481. Wall Map of the Natural History of the Mineral 

 Kingdom, by Dr. G. Seelhorst. P. C. Geissler, Number g. 



The wall map consists of coloured plates, which are mounted on linen, with a 

 portfolio in which to keep the map when not hanging on a wall. The text is 

 printed on both sides of the map. The map is constructed to fold up in the 

 portfolio, as well as to hang on a wall, and consists of one sheet. 



3482. Diagrams (four), or " epures," illustrative of Appli- 

 cations of Descriptive Geometry to Crystallography, viz. : 

 two illustrating derivation of holohedral and hemihedral tesseral 

 forms ; and two showing construction of crystal projections from 

 angular measurements and from crystallographic formulae. 



Prof. Jos. P. O'Neill?/. 



3483. Model, mounted with movable arcs and core, for 

 demonstration of the fundamental forms in each crystalline system, 

 and of the geometric method of derivation of the different holohedral 

 and hemihedral forms from the fundamental one in each system. 



Prof. Jos. P. O'Reilly. 



The model possesses a movable core adapting itself to the six systems an$ 

 rise of elastic cords to represent the intersections and edges of forms. 



