1914.] NATURAL SCIENCES OF PHILADELPHIA. 561 



wall of the crater referred to above more than 100 feet out of its 

 proper position. What could be more natural under these conditions 

 than that we would have found nothing in the centre of the crater 

 except some little pieces of iron oxide representing largely sparks 

 or bits of metal which were literally torn off the projectile as it 

 advanced through the rock target? By far the greater portion of it 

 must have held together, as a charge of shot holds together for a 

 short distance after it leaves the muzzle of a shotgun. It is con- 

 sidered extremely likely that the major portion of the mass lies 

 under the southern wall of the crater and particularly under that 

 portion of it which has been uplifted in the manner that I have 

 attempted to describe. 



The theory has been advanced that this great crater was par- 

 tially formed by the heating of the water in the moist sandstone 

 converting it almost instantly into steam. I have no doubt that 

 this action contributed in a measure to excavate the crater, but 

 I do not think that it contributed very largely to the general effect. 

 It seems to me that it is hardly necessary to call in any other agency 

 to account for the observed facts than the excavating effect of such 

 a projectile. In short I believe the crater would have been prac- 

 tically as large as it is to-day if there had been no water in the sand- 

 stone. We well know from repeated .borings by the Atchison, 

 Topeka & Santa Fe R. R. Company that these strata contain very 

 little water to-day and all the evidence is in favor of the crater's 

 being of recent origin, the Indians of that section having a legend 

 connected with the fall. 



Having once been convinced of the correctness of the impact 

 theory of origin, the size of the meteoric mass which formed the pro- 

 jectile becomes of interest. It is hardly conceivable that its weight 

 was less than five million tons. It may have been 10,000,000 tons, 

 or twice that weight. Admitting that it was a cluster that produced 

 the result, the wonder is that it was as small as we now realize it 

 must have l^een. These masses of meteoric material we know to be 

 flying through space in the vicinity of our solar system. They pos- 

 sibly represent the small remaining portions of the nebula out of 

 which our system was made. Most of them have probably long 

 since been gathered into the sun or into some of the planetary bodies. 

 Saturn's rings, I believe, are largely composed of meteorites. They 

 probably present an early stage of moon-making. The craters on the 

 moon's surface are much more thinkable in size than the Arizona crater. 

 Most of the craters on the moon's surface, which I firmly believe to 



