244 



Mr. William Phillips on the 



Substance. 



Primitive Crystal. 



References to Plate 12. 



Measurements. 



According to 

 Hauy. 



Accord- 

 ing to 

 Bournon 



By the 

 Reflecting 

 Goniometer 



Cyanite 



An oblique prism of ~i 

 which the plane P is very £• 

 nearly a rhomb. Haiiy. J 



Fig. 7. M on T 



M or T on the ad- 

 jacent plane, over 

 the edge A. 



IO60 6' 





106° 15' 

 73° 45' 



Corundum 



A slightly acute rhom- 1 

 boid. Haiiy & Bournon. $ 



Fig. 3. PonP 

 Pon P' 



86° 38' 

 93° 22' 



86° 

 94° 



86° 4' 

 93" 56' 







Sulphate of 

 Strontian 



A right prism with ) 

 rhombic bases. Haiiy. J 



Fig. 2 M on M 



M on the adjacent 

 plane, over the edge 

 A. 



104° 48' 

 75° 12' 





104° 

 76° 



Carbonate of 

 Lead 



An octohedron, of which ~) 

 the common base of the £ 

 pyramids is rectangular. J 

 Haiiy. 



A rectangular tetrahe- 

 dral prism with square 

 bases. Bournon. 



Fig. 8. Mon the opposed^ 



plane over theV 



apex 3 



M on M 



P on its opposedT 



plane over the > 



apex 3 



P on P 



70° 30' 

 62° 56' 



, • • 



71° 40' 

 108° 20' 



62° 42' 

 117° 18' 



Sulphate of 

 Lead 



A rectangular octohe- 7 

 dron. Haiiy. £ 

 Aright tetrahedral rhom- ~% 

 boidal prism with rhombic v 

 bases. Bournon. 3 



A right prism with 7 

 rhombic bases. W. P. J 



Fie 9 P ' on P ' 

 * 8 ' * P on P 



Fig. 11. P on P 



P on the adjacent 

 plane over the edge a. 



Fig. 13. P'onP' 



P' on the adjacent 

 plane over the edge a 



78° 28' 

 109° 18' 



101° 30' 

 78° 30' 



76° 18* 

 103° 42' 







Oxide of Tin. 



PI. 12. Fig. 1. 

 The crystals of this substance admit of cleavage parallel with all 

 the sides of the common prism, and of its diagonals, as well as the 

 faces of the primitive octohedron, which is obtuse. The first is 



