220 HISTORY OF MINERALOGY. 



says, in his preface to his Essais de Cristallograpliie, 

 " by the works of the celebrated Von Linnee, how 

 greatly the study of the angular form of crystals 

 might become interesting, and fitted to extend the 

 sphere of our mineralogical knowledge, I have fol- 

 lowed them in all their metamorphoses with the 

 most scrupulous attention." The views of Linnaeus, . 

 as to the importance of this character, had indeed 

 been adopted by several others ; as John Hill, the 

 king's gardener at Kew, who, in 1777, published 

 his Spathogenesia ; and Grignon, who, in 1775, 

 says, " These crystallizations may give the means of 

 finding a new theory of the generation of crystalline 

 gems." 



The circumstance which threw so much difficulty 

 in the way of those who tried to follow out this 

 thought was, that in consequence of the apparent 

 irregularity of crystals, arising from the extension 

 or contraction of particular sides of the figure, each 

 kind of substance may really appear under many 

 different forms, connected with each other by cer- 

 tain geometrical relations. These may be conceived 

 by considering a certain fundamental form to be 

 cut into new forms in particular ways. Thus if we 

 take a cube, and cut off all the eight corners, till 

 the original faces disappear, we make it an octohe- 

 dron ; and if we stop short of this, we have a figure 

 of fourteen faces, which has been called a cubo-octo- 

 hedron. The first person who appears distinctly to 

 have conceived this truncation of angles and edges, 



