CRYSTALLOGRAPHY MINERALOGY. 31? 



thermic characters, or with the cohesion, elasticity, magnetic and 

 electric properties of crystals, we should have to consider the 

 modes of using many forms of apparatus which more immediately 

 belong to the department of Physics, and less exclusively to that of 

 Crystallography than is the casein crystallographic optical research. 



We may therefore proceed to consider the apparatus necessary 

 for the pursuit of Mineralogy, and especially such as has an edu- 

 cational character. 



In so far as the most important fundamental character in a 

 mineral must be recognised in its chemical composition, Mine- 

 ralogy falls under the domain of Chemistry ; and the methods and 

 apparatus of the inorganic chemical analyst equally belong to the 

 two sciences, while their description naturally belongs to that of 

 chemical apparatus. But the importance of Mineralogy to the 

 miner has invested the portable and ready methods for examina- 

 tion of minerals afforded by the blowpipe, and a few physical 

 implements that usually are associated with it, with considerable 

 practical interest, and also with some educational consideration ; 

 and Freiberg has long been unrivalled both in teaching these 

 methods and in providing the apparatus for applying them. To 

 the mineralogist, however, still belongs from the hesitation of 

 chemists in general to appreciate the bearings of Crystallography 

 on their science the study and the . teaching of what may be 

 termed the science of chemical morphology; for to the mine- 

 ralogist this science is essential. 



Admirable models, representing all the varieties of crystal sym- 

 metry and crystal form, are now constructed in soft wood and sold 

 for a price that is remarkably low, considering the accuracy with 

 which they are cut. Diagrams illustrating crystallographic forms, 

 and wire models representing the planes of crystallographic sym- 

 metry and their axes, or illustrating hypotheses regarding the 

 molecular constitution of crystals, are needed for the intelligent 

 teaching of the subject. Useful also would be representations, 

 whether by diagram or by model, of the optical characteristics of 



