MERRILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 489 



cussed the physical aspects of the crater with reference to its similar- 

 ity to those produced by projectiles, and also discussed Mr. Gilbert's 

 hypothesis, the distribution of the iron and magnetic oxide about 

 the hole, the crater rim and interior, and the disintegrated sandstone. 

 His conclusions were that (p. 910) : (1) at this locality there is a 

 great hole or crater corresponding in all respects except size with 

 impact craters formed by projectiles of considerable size moving 

 at considerable velocities; (2) that in and about the hole and to a 

 distance of over 1,400 feet below the present surface of the plain 

 "every indication of either volcanic or hot-spring action was posi- 

 tively absent;" (3) that all signs which might be expected of the 

 impact of a great projectile were present ; (4 and 5) that the meteoric 

 material scattered about the hole and over the plain was deposited 

 at the same instant of time at which the hole was made; (6) that 

 in and around the hole is a quantity of material such as could be 

 produced only by a violent blow ; and, finally, that all the attendant 

 minor phenomena observed can be explained upon the theory of the 

 impact of a great projectile and none can be satisfactorily explained 

 upon any other theory. In view of these facts, Mr. Tilghman felt 

 himself justified in announcing that the formation of the crater "is 

 due to the impact of a meteor of enormous and hitherto-unprece- 

 dented size." 



With these conclusions the present writer freely confesses he was 

 not at first inclined to agree. In several minor matters, as that 

 relating to the origin of the iron shale and shale balls, he is still at 

 variance with them; but after going over the ground with both 

 gentlemen, noting the results of the borings, and restudying the 

 problem from all standpoints, he gives the following summary of his. 

 conclusions : 



VIII. Summary 



Consideration of Evidence. — So far as shape is concerned, the 

 crater could have been formed equally well by blow-out or impact. 



The character of a portion of the ejected material points, how- 

 ever, strongly to an origin by impact. It is difficult, if not impossible, 

 to conceive of the smashing and metamorphism of the sandstone on 

 any other ground. The sand grains are crushed in a manner that 

 could be brought about only by some sudden shock, such as might 

 possibly be imparted by an explosion of dynamite, but certainly not 

 by steam. The secondary foliation at an angle with the bedding 

 and the condition of molecular strain of the altered quartz indicate., 

 pressure, while the fused quartz indicates great heat. The latter 



