Mr. W. J. Sell and Prof. W. J. Lewis. [Feb. 14, 



The planes m, n, and c, though, as a rule, much more largely 

 developed than any others, were somewhat imperfect and often gave 

 several images. Hence it has been necessary to combine all the 

 observations in order to obtain satisfactory elements. The following 

 elements were ultimately selected, as those which agreed best with the 

 observations. From these elements the axial constants commonly used 

 by Continental crystallographers have been determined, and they and 

 a table of computed and observed angles are subjoined : 



FIG. 3. 



Forms observed (fig. 3) : a{100}, i{110}, n{UO} 2 

 c{001}, Z{011}, fc{012}, <2{021j, ^{312}, 



Elements: (100, 110) 38 33'j (110, 010) 32 2f; 

 (010, Oil) 40 29' ; (Oil, 001) 43 5' ; 

 (001, 101) 35 27' ; (101, 100; 40 21'. 



or A = 88 5f; B = 77 10'; C = 71 33', 



and a : I : c = T20406 : 1 : 1'0238. 



