1905.] NATURAL SCIENCES OF PHILADELPHIA. 889 



hole that would allow for a large buried meteorite in the latter, l)ut 

 that it is short by many, at least several million, cubic yards of the 

 quantity necessary to fill the hole at all. This, of course, if correct, 

 and of that the author has no doubt, entirely destroys the weight 

 of Professor Gilbert's reasoning, which was based on the assumed 

 fact that everything ejected from the hole still remained around it. 

 The solution is, of course, that in the time since the impact the rim 

 has been reduced to its present dimensions by erosion, and the reason 

 why it is or was so particularly subject to erosion will be taken up later 

 when the formations of the rim are discussed more in detail. 



As to the absence of sufficient magnetic perturbation, this is on its 

 face a much more serious objection, as it undouJDtedly proves the 

 absence of any one large mass of iron near the locality, whether mag- 

 netized itself or only magnetized by the induction of the earth's mag- 

 netism, and also the absence of a mass of fragments of a magnetically 

 neutral but magnetically permeable character magnetized by the induc- 

 tive action of the earth. But it would have no bearing whatever as 

 to the presence or absence of a mass of magnetized fragments each 

 having sufficient coercive force of its own to be independent of the 

 earth's inductive action, to the extent at least of retaining its own 

 proper polarity irrespective of the position in which it is placed in 

 regard to the terrestrial magnetic field. Such a mass of polarized 

 fragments would form a series of closed magnetic circuits with prac- 

 tically no external field whatever. In support of this the following 

 experiment was made. Two little cubes of magnetite about half an 

 inch on one side were taken, which, as nearly as could be observed, 

 had about the same effect on the magnetic needle. The weaker of the 

 two, if there was any difference, was preserved intact, and the stronger 

 was carefully broken up without loss to about the size of coarse sand. 

 These fragments were then packed in a paper case but little larger than 

 the original piece had been. It was found that this had to be approach- 

 ed to within an eighth of an inch of the compass needle to produce the 

 same deflection that the original piece did at eight inches. Not only 

 this, but it was found that one single grain of the sand-like fragments 

 of the pulverized magnetite had more effect upon the compass needle 

 when taken alone than the whole mass of them had when taken to- 

 gether. If the attraction of the mass of fragments of the supposed 

 iron meteorite could be reduced in this proportion to its normal attrac- 

 tion when in a single piece, it might, on Professor Gilbert's own figures, 

 lie within a very short distance of the surface of the present bottom of 

 the hole. 



