42 MAGIE— PHYSICAL NOTES ON [April 22, 



sembling fragments of shale, so that it has been called by Mr. D. M. 

 Barringer and Mr. B. C. Tilghman, who first recognized its meteoric 

 origin, shale ball iron. 



Through the kindness of the Standard Iron Company the author 

 was given an opportunity to visit and study Meteor Crater. In 

 this paper he desires to present the results of some of his observa- 

 tions, which have to do with physical problems presented by the 

 crater. The description of the crater from the more general point 

 of view, as a geological or cosmical phenomenon, has been given by 

 Dr. G. K. Gilbert, of the U, S. Geological Survey, and by others. 

 The demonstration that it owes its origin to the impact of a meteorite 

 or group of meteorites was made by Mr. Barringer and Mr. Tilgh- 

 man in papers presented to the Academy of Natural Sciences of 

 Philadelphia, December, 1905, and with additional evidence by Mr. 

 Barringer in a paper presented to the National Academy of Sciences, 

 November, 1909. Professor H. L. Fairchild, of Rochester, and 

 Mr. George P. Merrill, of the U. S. National Museum, have also 

 studied the crater from this point of view. 



2. Magnetism. — A cylinder 9 cm. long, 1.8 cm. in diameter was 

 cut out of a Canyon Diablo iron, and tested for its magnetic perme- 

 ability with a permeameter. The method is rough and unsatis- 

 factory, but the only one which can be employed without either 

 wasting too much work on shaping the specimen or possibly altering 

 its condition by heating and working it. The values of H, the 

 strength of field, and of /x, the magnetic permeability, are given in 

 the following table, taken from the curve which best represents the 

 observations. 



Tests with a similar cylinder of Norway iron gave values for /x 

 about double these, so far as the observations could be carried. 



The pieces of shale ball iron at the author's disposal could not be 

 prepared for the test with the permeameter. All that could be done 



