204 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vol. 50 



has to do principally with a singular type of meteoric iron which for 

 evident reasons was overlooked by earlier observers. 



In stating the facts bearing upon the origin of the crater, Mr. Bar- 

 ringer 1 writes of disinterring from pits and open cuts numerous 

 nodular masses of oxidized meteoric material, or "shale balls" of all 

 weights up to fifty pounds. These were usually roughly globular in 

 outline, and consisted exteriorly of hydrated oxide, of iron which 

 served as a cement, loosely binding together the adjacent rock frag- 

 ments (see pis. xviii and xix). In a number of instances such were 

 found to contain still unoxidized iron centers or nuclei, the inter- 

 mediate zone showing a green hydroxide of nickel mingled with 

 oxides of iron. Several of these "shale balls" were given the writer 

 for examination and study, and it is to them in particular and their 

 bearing upon the problem that the present paper has reference. 



The occurrence of the balls is sufficiently described in the paper 

 of Mr. Barringer. The writer, while on the ground, saw several of 

 them exhumed, and can corroborate his description in every detail. 

 It will be well, incidentally, however, to emphasize the fact that the 

 balls with iron centers have been found mainly on the north side of 

 the crater and in the trenches, rarely on the surface. 2 The apparent 

 significance of this will appear later. 



The appearance of the freshly exhumed shale ball is that of a 

 rough and friable mass of iron oxide encrusted with bits of sandstone 

 and limestone, and in the case of those found but a short distance 

 below the surface, thicklv entangled with grass roots (pi. xviii, 

 fig. 1). 



In the case of the smaller, superficial masses, oxidation has usually 

 progressed to the extent that no metallic residue remains, and the 

 nodule quickly falls to pieces on exposure. The larger and deeper- 

 seated nodules, as their weights indicate, still retain unaltered nuclei. 

 Such, cut in halves, are shown in fig. 2, pi. xviii, and figs. 1 and 2. 

 pi. xix. The rounded mass of iron is surrounded by a crust of 

 oxide, some 10 to 15 mm. in thickness. Mr. Tassin's examinations 

 show this oxide to consist of both limonite and turgite. Beyond this 

 is an indefinite zone of iron oxide and rock fragments. The inner 

 zone of oxide is identical in composition and physical properties with 

 much of the iron shale so common on the surrounding surface, and 

 suggests at once a like origin for both. An etched surface of the 



1 Proc. Acad. Nat. Sci. Phila., 1905, pp. 878, 879. 



2 Since the above was put in type Mr. Barringer has informed the writer 

 that one shale ball has been found on the east side of the crater, and one com- 

 pletely oxidized form on the south. 



