I9I0.] METEOR CRATER, ARIZONA. 45 



prevailing winds, is an area of brown sand, which the borings prove 

 has come from the depths of the crater. The central line at right 

 angles to this axis crosses the rim at or near the middle of two 

 opposite areas on which the ejected material is deposited in large 

 boulders, mostly of limestone, coming from the upper stratum of 

 the formation. In two lines from the center 33° west and 42° 

 east of this axis, toward the south, there lie out on the plain rows 

 of limestone boulders, marked on the map as the furthest thrown 

 limestone boulders. 



The map showing the effect of the disturbance on the original 

 strata exhibits this symmetry in another way. Starting where the 

 axis crosses the northern rim, where the strata are inclined at 

 only 5°, and proceeding around the rim in either direction, the 

 strata gradually tilt more and more, reaching an inclination on one 

 side of 50°, on the other of 80°. At about 135° around the rim 

 on either side we find a fault and a short stretch in which the 

 strata stand vertically. These two narrow regions are ended by 

 faults which separate them from the remaining part of the rim, 

 through the middle of which the south end of the axis passes. This 

 portion of the rim is simply lifted about 100 ft. and the inclination 

 of the strata is 0°. The lines of the furthest thrown limestone 

 boulders are nearly over the two regions in which the strata are 

 vertical. 



The experiment was tried of shooting a half inch spherical lead 

 ball from a high-power rifle into a level floor of smooth densely 

 packed silica. The inclination of the shot was about 30° from the 

 vertical. The tilting of strata, of course, could not be observed ; 

 but the distribution of ejected matter on either side of the plane 

 of incidence was remarkably like that described in the preceding 

 account of the crater. The greatest amount of finely powdered 

 material formed a rim to the shallow hole, ahead of the bullet. The 

 edge over which the bullet passed had little or no matter piled up 

 on it. The edges diametrically opposite, across the line of flight, 

 were lined with powder and many lumps of silica, still forming 

 definite masses, though the material is so friable that it was hard 

 to pick up one of these lumps with the fingers without crushing 



