558 . PROCEEDINGS OF THE ACADEMY OF [Sept., 



Professor Elihu Thomson has given me permission to quote a 

 statement which he made to me in a letter written a few days after 

 he visited the crater some years ago, as follows: "This Arizona 

 crater bears all the evidences of impact and the evidences of nothing 

 else." This is the complete story told in a few words. It will 

 be in the interest of science if scientific men, and especially those of 

 the United States Geological Survey who deny this theory of origin, 

 will present their reasons for maintaining the hypothesis that the 

 crater was due to some manifestation of volcanic activity. I believe 

 that it will be easy to refute any argument they may advance. No 

 examination of the crater since the exploratory work was done has 

 been made by any members of the Survey, to the best of my knowl- 

 edge and belief. Therefore, unless they can satisfactorily account 

 for the facts which I have stated in this and in my previous papers 

 on the subject on some other theory than that of impact by a great 

 mass of meteoric iron, it would seem that I can fairly claim to have 

 proved the theory that the crater was formed by this SLgency. 



There is good reason to believe that the meteoric mass was a 

 dense cluster of iron meteorites and possibly was the head of a small 

 comet which was not moving at very high speed, astronomically 

 considered, since there is no evidence, beyond the very slight evi- 

 dence referred to above, of the volatilization of any portion of the 

 mass. Moreover, it is certain that the siliceous limestone bed, which 

 it encountered after passing through the 40 to 50 feet of overlying 

 purplish-red sandstone, would have been readily fused had the 

 impact been such as we can reasonably suppose it to have been had 

 there been a head-on collision between this small cluster of iron 

 meteorites or cometary body and the earth. Besides this, as anyone 

 who knows anything about ballistics will at once acknowledge, there 

 would have been no such penetration as we now know took place: 

 nearly, if not fully, 1,200 feet into solid limestone and sandstone 

 strata. It has been inferred, therefore, that the cluster of iron 

 meteorites may have followed after the earth and that the blow de- 

 livered was not such as it would have been if there had been a direct 

 head-on collision. We now know that the mass, probably weighing 

 as much as 10,000,000 tons, if not more, penetrated through the 

 white or gray sandstone and as far down as the top of the Ked Beds 

 sandstone (Red Wall sandstone of the Grand Canyon section). 

 Several cores from this sandstone bed, showing it to be undisturbed 

 and lying in a horizontal position, have been brought up by the 

 drill directly under the centre of the floor of the crater and at a 



