44 MAGIE— PHYSICAL NOTES ON [April 22, 



of the magnetic dip, using a Kew Dip Circle. The mean vakie of 

 the dip found by fifteen observations was 62° 'J.j' , with maximum 

 variations at different points from the mean of — 5.1', and +4.2'. 

 These variations may have been due to errors of observation, but 

 are probably to some extent real and due to local conditions. There 

 are several drill holes in the floor of the crater in which the iron 

 pipes used in sinking the holes were abandoned, and these pipes 

 could easily modify the general field to such an extent as to account 

 for the different values of the dip which were found. 



If the size of the meteor by which the crater was made is esti- 

 mated by the old rules of artillery practice, we should conclude that 

 it is equivalent to a sphere of about 750 ft. in diameter. A sphere 

 of iron of this size at the appropriate depth below the floor of the 

 crater would seriously affect the magnetic field. Even on the more 

 moderate estimates of Mr. Barringer and Mr. Tilghman that it is 

 equivalent to a sphere 250 ft. in diameter, the values of the dip at 

 the extreme stations, at which the dip was observed, should differ 

 by 30'. That no such difference was found argues that the meteor 

 was broken and scattered by the impact, or more probably, as Mr. 

 Barringer strongly argues in his latest paper, was a cluster or 

 swarm of small masses of iron, mostly of the shale ball variety. 

 The possible intrinsic magnetism of these masses, coupled with the 

 possibility that they have gradually oxidized in the depths of the 

 crater, would account for the absence of any observed mag- 

 netic field. 



3. Mechanical Effect of the Impact. — When the map of the 

 crater, showing the distribution of the ejected material, is studied, 

 a remarkable symmetry of distribution is immediately apparent. 

 A line drawn through the center of the crater, 13° west of north, 

 can be taken as an axis of symmetry. This line on the north rim 

 of the crater passes through or near the lowest part of the rim, 

 and the region where the least ejected material is found. Its other 

 end on the south rim passes through the middle of the greatest 

 bulk of ejected material, which is furthermore found there in 

 small fragments or largely in the form of pulverized sandstone, or 

 *' silica." Just to the east of it, where it has been driven by the 



