198 



dicularface at the left hand* end is parallel to the diagonal 

 division of the nucleus, and the oblique fracture is parallel 

 to one of the faces of the rhomboidal prism ; the perpendi^ 

 cular lines indicate a continuance of the diagonal fracture, 

 the others a continuation of the rhomboidal fracture. These 

 are extended in the specimen more or less perceptibly until 

 lost in small nuclei, at the right hand end of the crystalli- 

 zation. 



The third figure may help to familiarise these things by 

 its being placed in another position, and showing similar 

 facts. The lower figure shows the geometrical divisions of 

 the nucleus into two molecules, by means of this fracture 

 parallel to the shortest diagonal of the rhomb. 



Having seen this, we cannot doubt the opinion of Haiiy^ 

 that there may be a fracture parallel to the longer diagonal, 

 dividing the molecules above mentioned into two : thus four 

 upright triangular prisms form the rhomboidal prism or 

 nucleus, each being an integrant molecule. 



* The faces at this end are all fractured ones. 



