Introduction to the Study of Mineralogy, 46Q 



After having presented the picture of the characters, the 

 assemblage of which distinguishes the species^ and the series 

 of the varieties which subdivide it, I have added annotations 

 which contain as it were its history. Here will be found 

 the indication of its principal situations in (he earth, and 

 that of the substances which most generally accompany it. 

 I afterwards detail the various opinions which have been en- 

 tertained as to the nature of the mineral which constitutes it ; 

 and I thought that it would not be useless to explain, when 

 I had an opportunity, what appeared to have deceived former 

 observers, and how the transition from error to truth was 

 effected. Here again naturally comes the explanation of the 

 phenomena which the mineral is susceptible of presenting, 

 in the event of its enjoying Some interesting property. I 

 shall be the more respected by my readers, when I inform 

 them that, in my applications of the subject to the mechani- 

 cal and healing arts, I have been furnished with valuable 

 assistance by M. Chaptal in the former department, and 

 M. Halle in the latter. 



The point of view under which I have considered mine- 

 ralogy in this treatise, required that the reader should be 

 prepared for the study of the method, by a detail of the 

 knowledge which was resorted to in forming the plan. I 

 have paid every attention to fulfilling this object in a series 

 of details, in which I develop the principles proper for clear- 

 ing up the entrance upon the science. T have presented in 

 two ways, the theory of the laws to which the structure of 

 crystals is subjected ; the one by simple reasoning aided by 

 figures, which render sensible to the eye the mechanism of 

 this structure; the other ill a, separate article, by the aid of 

 mathematical analysis, by giving to the results the whole 

 generality which the subject requires *, 



I ought 



know. I have found several, which will be pointed out in this treatise ; and 

 I am persuaded that we shall succeed, after continued inquiries, to augment 

 the number considerably. 



* I am far from thinking that the numerous applications which I have 

 made of this theory to the crystals examined by me; possess all the same degree 

 of exactness. The difficulty of determining, in several of these crystals, the 

 true direction of the natural joinings, the smallness of others, the defects 



G g 3 which, 



