756 SEC. 17. MINERALOGY, CRYSTALLOGRAPHY, ETC. 



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. Niclwlas 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, hemikedral, and tetra- 

 hedral forms, showing their orientation and combination with the 

 form 111 written. Made by contributor. 



Rev. Nicholas Brady, M.A. 



3493. Large Models of Crystals, for lecture illustration. 



Professor Crum Brown, University of Edinburgh. 



The models are made of pasteboard, and painted. Six models are sent 



(1) Rhombic Dodecahedron, and (2) Pentagonal Dodecahedron, illustrating 



the relation of these forms to the cube ; (3) and (4), Dextro and Laevo- 



tartaric acid ; (5) Double laevo-tartrate of soda and ammonia; (6) Asparagine. 



3494. Collection of 114 Models of Crystals, in wood. 



Heinrich Piel, Bonn. 



3495. Collection of 100 Models of Crystals, in wood, to 

 illustrate the most important chemical compounds. 



Heinrich Piel, Bonn. 



3496. Complete collection of Models of Crystals, 300, in 

 three boxes. Heinrich Piel, Bonn. 



3497. Collection of 30 Models of Crystals, of complicated 

 forms. Heinrich Piel, Bonn. 



The whole of the collections of the models of crystals have been carefully 

 prepared by hand, without the aid of machinery. 



The models of these collections have an average diameter of section of 

 5 centimeters ; if required, the models may also be procured of a section 

 of 10 centimeters, by which the price would be proportionately increased. 

 Besides complete collections of any desired size and number, single models 

 may also be obtained, the price of which will depend on the number of faces 

 and the difficulty of their manufacture. If desired, stands may be obtained. 

 Stands may be procured for exhibiting the models in a position parallel with 

 their axes. Each collection is accompanied by a catalogue containing, besides 

 the name of the model, its form and its crystallographic symbol according to 

 Naumann's system ; and, in addition to these, the most important minerals 

 and chemical compounds which the models represent. 



3498. Eighteen large Diagrams of Crystals. 



Prof. G. com Rath, Bonn. 



Theee diagrams are manuscript drawings, and are used for the illustration 

 of mineralogical and crystallographical lectures. 



