234 



Crystalloyrap hy . 



d. Wooden model of Mercui-ic Cyanide. 



Note. For fig of this model, see Per. Mat. Med., vol. i., p. 947, fig. 147. 

 The specimens c and d will be found in the upper compartment of the 

 central case, No. 9, facing the glass models. 



662. III. RHOMBOHEDRIC SYSTEM. (Hexahedral System. The 3 

 and 1 axed system.) 



a. Glass model (fig. 28), showing the following forms : 



White, rhombohedron, fig. 29. 



Blue, hexagonal scalenohedron, fig. 32. 



The whole of the model, hexagonal prism. 



Note. In this system there are three horizontal axes of equal length, 

 at angles of 60 to each other, and one vertical axis, either longer or 

 shorter than the other three, and placed at a right angle to them. In this, 

 as in all other glass models, the axes are indicated by red wires. 



b. Rhombohedron of Iceland Spar. 



Note. This specimen exhibits well the phenomenon of double refrac- 

 tion, as may be seen by looking at the single label placed beneath it. 



c. Wooden model of an hexagonal prism. 



d. Wooden model of a rhombohedron of Iceland Spar. 

 6G3. IV. RIGHT PRISMATIC SYSTEM. (Prismatic Trimetric System. 



1 and 1 axed system,.) 



a. Glass model (fig. 35), showing the following forms: 

 Yellow, octahedron with rhombic base (fig. 38). 

 Black lines on the glass, rhombic prism (fig. 39). 

 The whole of the model, rectangular prism (fig. 37). 

 Note. In this system all three axes are unequal in length, and placed 

 at right angles to each other. 



&. Crystals and half-crystals of Potassio-tartrate of 



Sodium. 

 Note. For fig. of these crystals, see Phillips' Transl. Pharm., p. 364. 



c. Rectangular prisms of Ferricyanide of Potassium. 



d. Right rhombic prisms of Citric Acid. 



Note. For fig. of these crystals, see Phillips' Transl. Pharrn., p. 96. 



e. Wooden model of Citric Acid. Two specimens. 



Note. One specimen resembles the crystals of the acid exhibited with 

 the felass models in the central case, and the other is figured in Phillip*' 

 Transl. Pharm., p. 96. They are right rhombic prisms. 



/. Wooden model of Rochelle Salt. Two specimens. 



Note. These specimens represent a crystal and a half crystal ; the 

 latter being the most common form of the salt. For fig., see Phillip*' 

 Transl. Pharm., p. 364, fig. 1, 2. 



g. Wooden model of Nitrate of Potassium. Two specimens. 



Note. For fig. of one of these specimens, see Per. Mat. Med., vol. i., 

 p. 540, fig. 87. ; the other model has one end of the right rhombic prism 

 terminating in a hexahedral summit. 



