226 HISTORY OF MINERALOGY. 



rallclique) which has one hundred and thirty-four 

 faces. 



In the course of a long life, he examined, with 

 considerable care, all the forms he could procure 

 of all kinds of mineral; and the interpretation which 

 he gave of the laws of those forms was, in many 

 cases, fixed, by means of a name applied to the 

 mineral in which the form occurred; thus, he intro- 

 duced such names as equiaxe, metastatique, uni- 

 binaire, perihexahedre, Usalterne, and others. It 

 is not now desirable to apply separate names to the 

 different forms of the same mineral species, but 

 these terms answered the purpose, at the time, of 

 making the subjects of study more definite. A 

 symbolical notation is the more convenient mode 

 of designating such forms, and such a notation 

 Haiiy invented ; but the symbols devised by him had 

 many inconveniences, and have since been super- 

 seded by the systems of other crystallographers. 



Another of Haliy's leading merits was, as we 

 have already intimated, to have shown, more clearly 

 than his predecessors had done, that the crystalline 

 angles of substances are a criterion of the sub- 

 stances; and that this is peculiarly true of the 

 angles of cleavage ; that is, the angles of those 

 edges which are obtained by cleaving a crystal in 

 two different directions ; a mode of division which 

 the structure of many kinds of crystals allowed him 

 to execute in the most complete manner. As an 

 instance of the employment of this criterion, I may 



