S2 Mr, R, Phillips on the [Feb. 



brother (Mr. W. Phillips) has presented me with the following 

 remarks : 



" In some treatises on mineralogy, the buntkupfererz is cited 

 as being found in cubes of which the solid angles are replaced, 

 and in cubes of which the planes are curvilinear. The AbbI 

 Haiiy, however, in his Traile, notices it under the name of 

 * cuivre pyriteux hepatique,' considering it as resulting from cop- 

 per pyrites, and, as it may be assumed, by some natural transi- 

 tion analogous to the known passage of the red oxide of copper 

 of Chessey into the green carbonate ; and he quotes it under 

 the same name as an appendix to. copper pyrites in his Tableau 

 Comparatif. 



** Being in the possession of a specimen from Cornwall, on which 

 there are many well defined and brilliant crystals, I detached 

 some, and have obtained from one of them, which is in the form 

 of the cube having all the solid angles replaced, the following 

 results by means of the reflective goniometer : 



fl on c 90^ 10' 



fl on c return 89 45 



aonb ^0 22 



a on b return 89 30 



con 6 1 90 8 



c on 6 return 89 42 



P'on P 109 40 



P' on a 125 16 



P' on c 125 



P' onh 125 35 



** If evidence were wanting to show that the crystal is in the 

 general form of the cube, it might be added that the average of 

 the six measurements a on 6 and c and their return planes, is so 

 near 90° as to amount to 89° 56', and that the planes P' F' 

 and their opposed planes, together with the plane a and its 

 return plane, may be measured by simply turning the crystal on 

 the axis of the goniometer so as to show each of those planes in 

 succession. 



" In attempting to cleave the crystals of this substance, I have 

 not been &o thoroughly successful as could be wished. Cleav- 



