896 SEC. 17. MINERALOGY, CRYSTALLOGRAPHY, ETC. 



emerald green ; three-faced octahedron and 12-faced scalenohedrons, deep 

 cadmium yellow ; 24-faced trapezohedron and three-faced tetrahedrons, burnt 

 sienna ; four-faced cube and pentagonal dodecahedrons, violet carmine ; six- 

 faced octahedron and six-faced tetrahedrons and irregular 24-faced trapezo- 

 hedrons, Schele's green. On the several zone circles are marked the position 

 of all the poles of the chief forms of the cubic system, except those of most 

 of the forms of h.k.l., or six-faced octahedron, which lie in the triangles made 

 by the zone circles. This model contains more than 700 wires soldered 

 together. Made by contributor. 



All these above forms are shown in solid in their corresponding colours in 

 the accompanying large series of models of the cubic system, and are drawn 

 in plan and perspective on a series of diagrams similarly coloured. 



The particular forms contained in this model are 100 ; 111 ; + and xrlll ; 

 110; 122 ; + and - K 122; 112; + and - K 112 ; 210; -i- and -TT 210; 

 531 ; + and TT 351 ; + and K 351 ; Miller's Terminology. 



3488. Collection of Models of the Cubic System of 

 Crystallography, to a scale of three inches for the circum- 

 scribing cube, made in cardboard, and painted according to their 

 simple forms. Rev. Nicholas Brady, M.A. 



These comprise all the chief varieties of the several species, both holohcdral 

 and hemihedral, together with the chief combinations of the principal examples 

 of each simple form, with the cube, octahedron, tetrahedron, and rhombic 

 dodecahedron, fully illustrating the passage of one combination to another. 

 In this series the positive and negative hemihedral forms and their orientation 

 are denoted by the dark and light tints of the same colour. 



3485. Diagrams illustrative of the Cubic System of Crys- 

 tallography, painted to match the models. 



Rev. Nicholas Brady, M.A. 



These give the general position on the sphere of projection of all the chief 

 varieties of the species in the system. Examples of the different species, 

 both holohedral and hemihedral, in orthographic perspective, in projection 

 on the plane of the paper, and giving the position of their poles on the sphere 

 of projection, with similar drawings for twin crystals, drawn by contributor. 



3489. Collection of three-inch Models of the regular Pla- 

 tonic Solids, the only forms possible with equilateral sides, and 

 equi- angular with the simple forms from which they are respec- 

 tively derived. Made by contributor. Rev. Nicholas Brady, M.A. 



3490. Set of Regular Octahedral Models, showing that 

 crystalline form depends upon the number and parallelism of parts, 

 and not upon the mere shape of the face. Made by contributor. 



Rev. Nicholas Brady, M.A. 



3491. Set of three-inch Models of the Pyramidal System 



of Crystallography, giving the chief simple forms of the minerals 

 of the system, with the latitude of their poles. Made by con- 

 tributor. Rev. Nicholas Brady, M.A. 



3492. Collection of Models of the Rhomb ohedral System 

 of Crystallography, with its holohedral, hemihedral^ and tetra- 



