230 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 2 



from the prevailing reddish color of the surrounding gibbers.^ 

 These " dikes " radiating outward from the crater immediately re- 

 minded the author of the " percussion figures " obtainable in mica 

 under suitable conditions. Although traces of similar ridges were 

 found around some of the other craters, particularly No. 4, none 

 were as well defined as those described around No. 3. The length of 

 these ridges varied considerably, but one could perhaps mention 30 

 yards as an average distance from the crater rim that a " dike " could 

 still be traced on the plain.* 



Another point of extreme interest was the discovery on the plain 

 to the north of the Main Crater of black glassy material greatly 

 resembling the glass of fulgurites. This is seen in some specimens 

 to be vesicular, in others to be cementing rock fragments. There is 

 little doubt that this has been formed by the fusing of the country 

 rock by the enormous heat of impact of the meteorite. It is a point 

 of interest that glassy siliceous matter apparently of similar origin 

 has been found at the great meteorite crater at Canyon Diablo in 

 Arizona. 



DIRECTION OF FALL 



Until the position of any iron masses buried in the craters has 

 been located, the direction of fall of the meteoritic bodies must be 

 more or less a matter of conjecture. There is, however, one point 

 which may give some indication of the direction in which the bodies 

 were traveling. Notes were made as to the general position of all 

 meteoritic specimens collected. From this it was seen that the 

 material was generally concentrated on the western side of the 

 craters (fig. 2). This was particularly noticeable in the case of 

 craters Nos. 3 and 4. Around these craters there seemed to be no 

 indication that such factors as prevailing winds or surface drainage 

 had favored the uncovering of meteoritic material on one side more 

 than the others. 



This fact is subject to two interpretations depending on whether 

 the majority of the fragments were formed by the impact having 

 a shattering effect on the larger masses, or whether the fragments 

 had existed separately for some time before landing. If the former 

 supposition is correct, one would expect that the fragments had been 

 deposited or "splashed" on the farther side of the crater; that is, 

 the meteoritic bodies possessed an east to west movement. If the 

 latter is the correct supposition, one would expect that the smaller 

 bodies, not possessing the momentum of the larger, would be im- 



' Gibber, aboriginal Australian for a large stone or bowlder. 



* Some of the craters of the moon (e. g., Copernicus) show somewhat similar radiating 

 ridges. This may, perhaps, lend some support to the theory that the lunar craters are of 

 loeteoric origin. 



