470 Introduction to the Study of Mineralogy . 



T ought not to omit how much I am indebted to the in- 

 telligence and assiduity of those who have traced the pro- 

 jections relative to crystallography, and to the theories which 

 flow from mineralogical science. The idea of this great work 

 was conceived by M. Brochant, mining engineer, who has 

 begun to realize it. Several other engineers and scientific 

 men have endeavoured to complete what he had begun. 

 M. Tremery, to whom belong, among other things, almost 

 all the projections depending upon calculation, which he 

 perfectly well understands, has carried into their execution 

 the intelligence and accuracy so necessary for enabling the 

 eye easily to catch the respective positions of the different 

 lines, the constructions of which form the whole. Messrs. 

 Cordier, Lefroy, Gallois, Houry, Depuch, Cressac, Du- 

 cros, and Hericart, have also given proofs of zeal and talent, 

 in the drawing of figures which relate to the different classes 

 of minerals. Such is the masterly manner in which they have 

 represented, relative to a nucleus which has constantly the 

 same position, the different secondary forms which are so 

 many modifications of it, that we perceive, as at one glance, 

 the relations of these forms, both with each other and with 

 their common nucleus : this is a kind of graphic treatise of 

 the laws to which the structure is subjected. 



The School of Mines has offered me another resource of 

 great value, on the subject of the very basis of my work. 

 Placed in an isolated situation for many years, and limited 

 to my own exertions, I occupied myself, in solitude, with 

 arranging the materials for my work ; with determining, by 

 observation and theory, all the crystalline forms which I 

 was able to procure ; ascending to the causes of the most 

 interesting phaenomena presented by minerals ; drawing, from 

 the properties of these bodies, characters proper for distin- 

 guishing them, and collecting every thing relative to their 

 history, &c. . 1 had even already traced the plan of their 



which, upon those of a more sensible volume, would alter the level of the 

 forces, are so manv causes of uncertainty, which ought to influence the solu- 

 tions of the problems. It is very probable, that observations subsequently 

 made under more favourable circumstances will serve to rectify several of 

 my data, and place the results of calculation on a par with those of N lture. 



methodical 



