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OF ARTS AND SCIENCES. 66 



was made to break the specimen parallel to one of these cracks, with 

 the expectation of getting the planes already described in the previous 

 iron. 



When the slab was mounted in the vice and struck with the hammer, 

 there at once appeared on the surface numerous very fine ci'acks 

 parallel to the two directions just mentioned, and at once suggesting 

 the two sets of fine parallel lines which are first brought out on an 

 etched surface of this iron but are obliterated by the continued action 

 of the acid. Finally, the slab broke, but exhibited only a single plane 

 through the entire extent of the fracture (33 mm. in length by 6 mm. 

 in breadth), and, instead of being striated, there was developed a very 

 striking flaky surface as if little thin layers had resisted the cleavage, 

 parting at last with irregular edges more or less separated from the 

 main surface. An attempt was next made to break the slab at right 

 angles to the first direction, in order to get other crystal faces ; but, 

 instead of breaking along the edge of the vice, as a Butcher specimen 

 readily would have done, the Saltillo iron broke again with the same 

 single cleavage plane, at right angles to the desired direction and 

 running directly down into the jaws of the vice, entirely regardless of 

 the way it had been clamped and the blows of the hammer applied. 



Every attempt to break the slab gave the same result. It would 

 only break in the two directions indicated by the first fine cracks, and 

 corresponding to the angle that a cube face makes with the adjacent 

 face of a twin cube^ and always broke along a single plane exhibiting the 

 flaky surface already mentioned. The only way of getting a different 

 fracture was to saw the specimen to a thin edge, and so force it to 

 break in the desired direction, and then it would present a surface of 

 fine cubes wholly different in character from the large striated faces 

 of the Butcher irons. 



Just at this time we received from "Ward and Howell a large slab 

 of a new meteorite found in Allen County, Kentucky, and the whole 

 character of this iron, including the etched surface, so closely resembled 

 the Coahuila specimens that we were interested to see whether it would 

 show any striking cleavage. Ward and Howell kindly furnished us 

 with some small slabs, and, on breaking them in the way already 

 described, they showed exactly the same characters as the Saltillo iron. 

 The fine parallel cracks appeared under the first blows of the hammer, 

 and then the slab broke regardless of the way it was clamped in only 

 the two directions at angles of about 132° and 53°, presenting a single 

 cleavage plane with the marked flaky appearance characteristic of the 

 Saltillo iron. 



VOL. XXIV. (N. S. XVI.) 3 



