MINERALOGY AND GEOLOGY. 



I. CRYSTALLOGRAPHY. 



MODELS OF CRYSTALS. 

 A. Wire Models. 



1. Wire models of the five regular solids. 



1860. Exhibited by J. R. LarJcin. 



Six inches in diameter. They comprise (1) the tetrahedron 

 the solid edges represented in blue wire, and those of the enclosed 

 octahedron in white wire ; (2) the cube in blue wire, with the 

 enclosed tetrahedron in white wire, and the hexagonal section of 

 the cube in green wire; (3) the octahedron in blue wire, the 

 combination of this form with the cube in white, and the 

 hexagonal section coinciding with the edges of the latter, in 

 green ; (4) the pentagonal dodecahedron in blue, and enclosed 

 cube in white; (5) the triangular icosihedron in blue, with 

 contained octahedron in white. These last two are not possible 

 crystallographic forms. 



2. Wire models of the five regular solids. 



1861. Exhibited by /. B. LarJcin. 



These are of 4-inch size, viz., tetrahedron, cube, octahedron, 

 pentagonal dodecahedron, and triangular icosihedron all repre- 

 sented by blue wires along the solid edges. 



3. Large wire model, containing an example of each 

 species of simple form in the cubic system of crystal- 

 lography, with its corresponding hemihedral forms 

 inscribed within a sphere of the chief zone circles of the 

 system. 



1876. Lent by Rev. Nicholas Brady, M.A. 



In this model, the lines meeting in the centre are the 

 crystallographic axes, those of quaternary symmetry are coloured 

 red, those of ternary symmetry blue, and those of binary sym- 

 metry green. Nineteen simple forms are represented by their 

 solid edges. Those of the cube are coloured vermilion, those of 



