OP ARTS AND SCIENCES. 



31 



hammer. The slab broke readily along the jaws of the vice, exhibit- 

 ing a superb crystalline cleavage, the faces of the crystals having a 

 most brilliant lustre, almost like antimony, and, though the iron was 

 soft enough to cut with a knife, yet some of the single cleavage faces 

 were nine or ten millimeters in extent. These crystal faces usually 

 formed angles of about 132°, or else right angles, though in some 

 parts there were sharp projecting points, formed by the meeting of 

 two rectangular planes with a third set obliquely. Furthermore, all 

 the faces were most beautifully striated by numerous sets of fine 

 parallel lines, easily distinguished by the eye, generally making angles 

 with each other of 127°, 90°, and 53° respectively, a few of the lines 

 appearing to be parallel to the intersections of the faces. 



Fig. 2 shows enlarged one set of crystal faces as they appeared on 

 the surface of fracture. The planes were absolutely perfect, and lar^e 

 enough to be readily measured with an application goniometer. Thus 



Fig. 2. 



Fig. 3. 



it was found that the plane B made with C a right angle, B and A an 

 angle of about 132°, A and C an angle of about 109°; and the small 

 plane D, set obliquely on the solid angle thus formed, made an angle 

 of about 125° with B and C, and 164° with A. The plane E and the 

 one parallel to it were the sawed faces of the slab. All the other 

 planes forming the surface of fracture were parallel to the ones shewn 

 in the figure, and they could all be referred to faces of the twin cube, 

 as shown in Fig. 3, where the corresponding faces are lettered the 

 same and placed in a parallel position. The striations already men- 

 tioned appeared most markedly on the face A, that being the largest, 

 and therefore the one most easily examined. 



Fig. 4 shows, on a large scale, this plane referred to the face of 

 a cube, only the most prominent of the striations being represented, 

 in order to preserve clearness in the figure. It will be seen by the 



