THE S TR UC TURK OF ME TE0R1 TES 1 8 7 



meteorites every gradation may be traced from metallic masses 

 in which the silicates appear as porphyritic ingredients, through 

 those appearing to be made up of interwoven constituents, to 

 those in which the metallic constituents appear as isolated 

 grains. In several of the latter class of meteorites (Farmington, 

 Crab Orchard Mountains, Bluff) long, branching, metal fila- 

 ments are seen to be associated with the isolated grains. 



In the view of the present writer, these are filamentous 

 phases of the structure of the metallic portions of the meteorite. 

 Other meteorites, of which those of Honolulu, Mocs, and Pultusk 

 may serve as illustrations, have what appear to be metallic veins 

 when seen in cross sections. When cleft along the vein, how- 

 ever, these prove to be slickensided surfaces along which the 

 metallic grains of the meteorite have been drawn or flattened 

 out by the movement. These vein-like structures are clearly of 

 different character from those just described. They sometimes 

 give a well-marked appearance of a vein outlined on the crusted 

 surface of a meteorite. This is owing to the fact that resisting 

 fusion more than the stony matter they stand out in relief. 



Cleavage and joints. — Most of the cubic irons are character- 

 ized by a complete cubic cleavage. This cleavage doubtless 

 indicates that the masses are crystal individuals. Huntington 

 has described cleavage planes as passing through some of the 

 octahedral irons independent of the octahedral structure. It is 

 probable that these, as well as cleavage along the octahedral 

 planes often noted, are separation planes resulting from weather- 

 ing. 



Few stone meteorites are of sufflcent size to exhibit a jointed 

 structure if it existed. Meunier has called attention to an 

 elongated depression in one of the L'Aigle stones which he 

 regards as marking the position of a former joint plane. The 

 Long Island meteorite, the largest stone meteorite known, 

 is cut by three large division planes which perhaps represent 

 joint planes. Two of them are at right angles to one another, 

 while the third, somewhat broken, is nearly at right angles to 

 the other two. The great irregularity of form of most meteorites, 



