1914.] NATURAL SCIENCES OF PHILADELPHIA. 557 



tinued, has Ix'cn known to produce sucli an effect. The only com- 

 parison which occurs to me and which will at all fit the facts is 

 that of the striking of a heavy armor-piercing projectile upon armor 

 plate. There, I understand, a very high heat is generated moment- 

 arily, as was certainly the case at the Arizona crater. There also 

 the heat of impact is sufficient to not only fuse a small portion of 

 the target, but a small portion of the projectile, since momentarily 

 iron-and-nickel vapor is produced. That this vapor of iron and 

 nickel was also produced at the crater, being derived from the 

 impacting body, is evidenced by the fact that this particular variety 

 of fused sandstone, referred to by me as "Variety B" of metamor- 

 phosed sandstone in my National Academy paper, is nearly always 

 more or less abundantly stained by iron and nickel oxide. The 

 fact that this stain is often found in places where the metamorphosed 

 sandstone has gaped open under the influence of intense heat and 

 then closed again upon cooling, is most significant. 



Now it must not be forgotten that the white or gray saccharoidal 

 sandstone, small portions of which have been fused in this way, 

 does not outcrop anywhere nearer than the Grand Canyon of the 

 Colorado, seventy miles distant, where it is known as the White 

 Wall or Cross-bedded sandstone and overlies, as at Meteor Crater, 

 the Red Wall or Red Beds sandstone. At the crater the upper 

 portion of this sandstone occupies a position about 350 feet below 

 the surface of the plain, being overlaid by about 300 feet of the 

 Aubrey limestone and 40 or 50 feet of the purplish-red sandstone, 

 wiiich, in the form of small buttes, is found all over the surrounding 

 otherwise almost level plain. It must be remembered also that all 

 the strata in this locality are horizontal. Clearly, nickeliferous 

 iron had penetrated into and, as we now have strong reason to 

 believe, through this bed of white or gray sandstone, and we know 

 that nothing terrestrial in this vicinity contains nickel in any form. 

 The only possible source of this stain is, therefore, the meteoric iron, 

 the occurrence of which has been very fully described in my previous 

 papers. (See Plate XXIII, showing the distribution of meteoric 

 iron around the crater.) It seems to me, therefore, that this 

 peculiar vesicular form of metamorphosed sandstone, which was 

 certainly produced by sudden and intense heat and which is so 

 abundantly stained with nickel and iron oxide, in itself furnishes an. 

 incontrovertible proof of the impact theory of origin, the opinion 

 of certain members of the United States Geological Survey to the 

 contrary notwithstanding. 



