232 



HISTORY OF MINERALOGY. 



surements were found very inaccurate by many suc- 

 ceeding crystallographers ; Mohs says l that they are 

 so generally inaccurate, that no confidence can be 

 placed in them. This was said, of course, according 

 to the more rigorous notions of accuracy to which 

 the establishment of Haiiy's system led. Among 

 the persons who principally laboured in ascertain- 

 ing, with precision, the crystalline angles of mine- 

 rals, were several Englishmen, especially Wollaston, 

 Phillips, and Brooke. Wollaston, by the invention 

 of his Reflecting Goniometer, placed an entirely 

 new degree of accuracy within the reach of the 

 crystallographer ; the angle of two faces being, in 

 this instrument, measured by means of the reflected 

 images of bright objects seen in them, so that the 

 measure is the more accurate the more minute the 

 faces are. In the use of this instrument, no one 

 was more laborious and successful than William 

 Phillips, W 7 hose power of apprehending the most 

 complex forms with steadiness and clearness, led 

 Wollaston to say that he had " a geometrical sense." 

 Phillips published a Treatise on Mineralogy, con- 

 taining a great collection of such determinations ; 

 and Mr. Brooke, a crystallographer of the same 

 exact and careful school, has also published several 

 works of the same kind. The precise measurement 

 of crystalline angles must be the familiar employ- 

 ment of all who study crystallography; and, there- 

 fore, any further enumeration of those who have 

 1 Marx. p. 153. 



