OF ARTS AND SCIENCES. 313 



XXV. 



FEATURES OF CRYSTALLINE GROWTH. 



By Oliver Whipple Huntington. 



Presented June 12, 1889. 



Variations in the Butcher Irons. 



In a former paper * the author discussed in some detail the crystal- 

 line structure of iron meteorites, and in a second f described the 

 cleavage exhibited by various specimens of the Coahuila group of 

 irons, which are generally supposed to have come from the same 

 original mass. It was then shown that in this group of irons the 

 Butcher specimens differed so markedly from those of Saltillo (Santa 

 Rosa) that the cleavage seemed to offer a conclusive means for separat- 

 ing the two falls, though the appearance of the etched surfaces failed 

 to distinguish them. 



As several very large individual masses of these irons are now in the 

 Harvard Cabinet, under the general name of " The Butcher Irons," 

 we were interested to see whether any peculiarity of structure would 

 further distinguish them as independent meteorites, or whether on the 

 contrary they could be identified as having unquestionably come from 

 the same original body. A careful examination of the exterior of 

 these irons showed that they had begun to break up since becoming 

 the property of Harvard College, but this alteration had only taken 

 place in certain parts of the specimens. The largest specimen seemed 

 to have a zone running through the thickest part from which could be 

 detached with little difficulty octahedral fragments of iron made up of 

 distinct plates, showing a cleavage very similar to the well known Put- 

 nam County iron, while the rest of the mass was compact and un- 

 altered. Thus certain parts of the Butcher specimens appeared to 

 have an entirely different structure from what we are accustomed to 

 associate with these irons. They have heretofore been known as 

 typical " cubic irons," and, though it has been shown that all the twin 



* Proceedings of the American Academy, vol. xxi. p. 478, May, 1886. 

 t Ibid., vol. xxiv. p. 30, October, 1888. 



