SCIENTIFIC KEW&, 237 



Crystallographic Models, exhibiting the forms of Crystals^ 

 their Production, Geometrical Structure, Transitions of Forms, 

 and mechanical Dissections. Intended to illustrate the Science 

 of Crystallography, after the Method of Haiiy, " Accompa- 

 nied with a Treatise elucidating the Elements of that Branch of 

 Knowledge. By Frederick Accum, M. R, T. A, Operative 

 Chemist and Lecturer on practical C hemistry, and on Mine- 

 ralogy and Pharmacy. 



'^Infuture the name of God, will be as distinctly written on a crystal, 

 as it has hitherto been in the Heavens." Philosoph. Journal, vol. 

 ix, p. 87. 



To Mr, Nicholson. 

 SIR, 



THE general attention which of late years has been paid to Cultivation of 

 the science of minerals cannot have escaped the notice "^ineralogical 



science 

 of the most superficial observers. No department of natural 



history has been cultivated vi^ith more ardour and success than 

 mineralogy, and in none have the cultivators of science been 

 more numerous, both at home and on the Continent. It em- 

 braces a wide circle of votaries among the curious and wealthy 

 classes of the community, and it is intimately connected with 

 that laudable passion for exploring the productions of nature 

 which characterises the age in which we live. 



Indeed, under whatever points of view we examine the shell Symmetrical 

 of our globe, we are struck with the variety of its productions, solids or cry- 

 When we cast our eye over the substances which compose the 

 collections of mineralogists, or the cabinets of the curious, we 

 behold a vast number ot bodies, which are regularly shaped, and 

 exhibit the forms of geometrical solids. The substances are 

 called crystals. 



When we examine the constitution of crystalline solids by General facts 



the methods of chemistry, we become convinced, that the same respecting 



' crystals. Vane- 



identical substance, or material, does assume different figures, ties in the same 

 which frequently bear no such resemblance to each other, as substance. 

 would seem to indicate their relation. And chemistry, or the 

 chemical art, is also capable of causing bodies to assume symme- 

 trical forms : and the figures of these are likewise liable to be 

 altered by circumstances, which affect the crystallizing process. 

 SugaiCflfldy; for example, usually crystallises in oblique four- 

 sided 



