364 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



The very interesting results given in Table XI were obtained by Mr. 

 John Coulson, who has helped me in all this work, with a standard 

 cylinder, 1.283 centimeters in diameter, made of Jessops Tool Steel. 

 This celebrated brand of steel seems harder under the file than the 

 Stubs or the Crescent Drill Rod, but is remarkably permeable, and has 

 been much used for permanent magnets. 



TABLE XI. 

 Cylinder of Jessops Round Tool Steel. 



My thanks are due to the Trustees of the Bache Fund of the 

 National Academy of Sciences who have kindly lent me some of the 

 apparatus used in making the observations described in this paper. 



The Jefferson Laboratory, 

 Cambridge, Mass. 



