256 /:'. Cohen — Meteoric Iron from Soudan. 



part of rlu 1 meteorite in question must at some time have been 

 Likewise naosl ox posed to the eroding action of the compressed 

 air. The two perforations require no special explanation. 

 Where they occur, the meteorite is so thin that the coincidence 

 of normal flat cavities on the breast and back sufficed for their 

 production. 



.V pronounced peculiarity of N'Goureyma, which one read- 

 ily observes in examining polished sections, is the enormous 

 number of small troilites and their regular arrangement, as 

 well as their quite uniform distribution. In sections parallel 

 to the length of the meteorite (Plate IY, fig. 1) these appear 

 mostly as needles, 1-| to ll mm long and \ to l-| mm thick ; or as 

 thick-set to elongated bars, sometimes tapering to the finest 

 threads. They also occur in the form of hook-shaped contor- 

 tions, fork-like bifurcations, ramifications, or wholly irregular 

 forms which, in those of smaller dimensions, diminish to mere 

 points. Whenever, in the section under consideration, there 

 is a club-like arrangement, the thicker end always lies toward 

 the pointed end of the meteorite, as though the troilite had 

 been drawn out in the direction of the motion. 



In sections at right angles to the length of the wedge 

 (Plate IY, fig. 2), on the other hand, the troilite stems invari- 

 ably occur in cross section, showing the greatest variety of 

 forms. Yery frequently they are rounded or, when larger, 

 elliptical. In either case the troilites are sometimes compact, 

 sometimes in the form of a hollow cylinder, the walls varying 

 from 0*1 to 0'3 mm in thickness, filled with nickeliferous iron. 

 Occasionally, however, the latter is divided into two equal 

 parts by a thin portion of troilite ; or sundry isolated cylinders 

 of iron occur in the troilite. Four of the latter, for exam- 

 ple, were observed in a troilite cylinder of 5/4 mm diameter. 

 Other sections show forms resembling crescents, horseshoes, 

 sickles, hooks, Ts, masses shaped like clubs or tadpoles taper- 

 ing to threads of 0'05 mm diameter, and are sometimes fashioned 

 into various strange hieroglyphics, such as occasionally appear 

 in schreibersite, but, so far as my knowledge extends, have never 

 heretofore been observed in the troilite of any meteoric iron. 



These forms on the two sections at right angles to each 

 other show that all the troilites are extended in the same 

 direction and are parallel ; forming an arrangement closely 

 resembling the fiuid structure of terrestrial rocks. One can 

 best form an opinion of the entirely unusual number of enclos- 

 ures, which of course are in part veiw small, when I state that 

 I have counted over 150 troilites on a surface of 12 sq cm and 

 that there is scarcely a surface of 05 sq cm to be found in which 

 they are entirely lacking. The distribution on any cross section 

 is always pretty uniform ; the total number, however, diminishes 

 appreciably toward the pointed end of the meteorite, as though 



