v i i i Introduction 



part of the volume differs much from the analytical 

 processes contained in the Abbe Haiiy's more com- 

 prehensive works.* 



When I first began to examine the crystalline forms 

 of minerals I was much assisted by a large collection 

 of the drawings of crystals, which was very kindly 

 lent me by my friend Mr. William Phillips. The 

 number and variety of the figures contained in this 

 collection was the immediate cause of the attempt to 

 reduce the forms of crystals into classes, and of the 

 construction of the tables of modifications already al- 

 luded to. Since that period, and particularly during 

 the printing of this volume, Mr. Phillips has fre- 

 quently assisted me by his communications relative to 

 the forms, the cleavages, and the measurements of 

 crystals, which I had not other means cf immediately 

 acquiring. 



During the course of my investigations I have fre- 

 quently found it necessary to consult larger collec- 

 tions of minerals than my own. On these occasions 

 I have generally referred to my friend Mr. Heuland, 

 and lam happy in the opportunity of acknowledging 

 the readiness and the liberality with which he has 

 invariably assisted my views, by permitting an access 

 at all times to his large and valuable cabinets, and 

 very frequently by contributing rare and interest- 

 ing specimens to mine which I could not otherwise 

 have acquired. 



I have sometimes sought information from the ex- 

 tensive cabinet in the British Museum, and have 



* Mr. Levy is at present engaged in an examination and description 

 of one of the finest collections of minerals in the kingdom, which be- 

 longs to C. H. Turner, Esq. The opportunity which this examination 

 will afford him of connecting a knowledge of the forms of crystals with 

 his well-known mathematical attainments, will enable him to convey 

 valuable instruction in this department of science to others, to which 

 object he intends to devote some portion of his time in future. 



