36 Mr. J. F, Daniell on Crystallization. 



Dr. Wollaston next proceeded to inquire what forms would 

 probably occur from the union of other solids most nearly allied 

 to the sphere ; and he showed that, by supposing the elemen- 

 tary particles to be spheroidical, many solids might be con- 

 structed which are well known to crystallographers. 



By imagining the axis of the elementary spheroid to be its 

 shortest dimension, a numerous class of well-known solids 

 originate. By grouping together oblate spheroids, in the same 

 manner as the spheres in the formation of the acute rhombo- 

 hedron, the resulting figure will still be a rhombohedron ; 

 but the measure of its angles will be different, and will be 

 more or less obtuse according to the degree of oblateness of 

 the original spheroid. If the proportion of the axis be as 1 to 

 2.87, the rhombohedron will be that of calcareous spar. 



If the degree of oblateness were as 1 to 2, a right-angled 

 rhombohedron or cube would result. These solids would 

 obviously be split, by mechanical force, in directions parallel to 

 their faces. 



If the elementary spheroid on the contrary were oblong in- 

 stead of oblate, it is evident that by mutual attraction their cen- 

 tres would approach nearest to each other when their axes are 



