THOMSON. — THE FALL OF A METEORITE. 723 



enough to cause rapid rusting after it entered the earth's atmosphere 

 and became subject to moisture. 



The plain around the crater has yielded numerous masses of the 

 iron, some of them several hundred pounds in weight, and one dis- 

 covered during the past summer weighs about 1700 pounds. 



The amount of rock blown out of the crater cavity could not have 

 been less than two or three hundred millions of tons, not considering 

 the large amount which fell back and which now lies at the bottom of 

 the bowl-shaped hollow of the crater. Nowhere else on the earth's 

 surface has meteoric iron been found so spread about. 



Yet there remains an unsolved problem. What became of the enor- 

 mous meteoric mass, or the cluster of them which was capable by its 

 impact of displacing so large an amount of rock 1 Allowing only one 

 ton to every 20 or 30 tons of ejected material, we still have about 10 

 millions of tons of meteoric iron to account for. This would constitute 

 a solid mass of between 400 and 500 feet in diameter. 



The attempts to explain this crater as the result of volcanic action, or 

 as produced by a steam explosion from below, are certainly to be re- 

 garded as rather far fetched in view of the presence and mode of occur- 

 rence of the meteoric irons, and the many evidences presented which 

 seem to me to lead inevitably to the conclusion that here indeed we 

 have a huge impact crater and that only. Tbe floor of the crater is 

 overlain with sedimentary deposits of an aquatic nature, the washing 

 of the walls and talus indicating the existence at some time of a small 

 lake or pond. Below this is a vast bed of mingled materials, mostly, 

 however, the pulverized white sandstone or " rock flour," the result of 

 crushing of the rock layers such as now surround it. 



For exploration a shaft has been sunk into this bed of a nearly pure 

 silica, but contrary to expectations it had to be discontinued. Water 

 was reached at about 200 feet below the crater floor and the extremely 

 fine silica rock flour thus became a most typical and troublesome quick- 

 sand and limited the depth of the shaft. Recourse was had to drill 

 holes, about 28 of which have been sunk to various depths not far from 

 the central area, and some of these have reached the underlying and 

 undisturbed red sandstone layer at about 850 feet below the crater 

 bottom. 



The material brought up has shown evidence of disseminated mete- 

 oric iron and nickel, but no large masses were found. Specimens of 

 the silica metamorphosed by heat and steam under pressure, causing a 

 partial aqueous fusion, have been secured. 



Careful magnetic tests conducted by Prof W. F. Magie, head of the 

 Physics Department at Princeton, have failed of result, probably because 



