THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. I. — On the Magnetic Properties at High Excitations 

 of a Remarkably Pure Specimen of Soft Norway Iron ; 

 by B. Osgood Peikce. 



Some mouths ago au electro-magnet was made for special 

 use in the Jefferson Laboratory which had the form of atoroid 

 uniformly wound with insulated wire for nineteen-twentieths 

 of its perimeter. The core was of stout iron rod bent into the 

 shape of a ring — complete except for a gap one centimeter 

 wide. The mean diameter of the core was about fifty centi- 

 meters and a meridian section of the iron had an area of about 

 twenty square centimeters. The exciting coil was made of 

 about thirty kilograms of 'No. 10 B. & S. wire and the magnet 

 had the general appearance indicated by figure 1, although the 

 turns of wire which show in the photograph belong to a short 

 test coil outside the winding proper. 



It is evident that, under the most favorable circumstances, 

 the leakage in the case of a magnet of these dimensions must 

 be very large, but when this magnet was tried its performance 

 fell so far below what, according to any known experience, it 

 ought to have been, that it was thought best to have the iron 

 tested both chemically and magnetically in the hope that the 

 information thus procured might prove valuable in future 

 designing. This seemed the more desirable since the core had 

 been obtained by Professor Trowbridge, the Director of the 

 Laboratory, in response to his inquiry for the very best brand 

 of soft Xorway iron to be had in the market. 



The chemical analysis made by Mr. Emile Raymond Riegel 

 showed this commercial iron to be of an extraordinary purity. 

 The tests for nickel, cobalt, manganese, tungsten, and for 

 "Groups IV and V" were all negative. There was less than 

 0'03 per cent of carbon, less than 0*047 per cent of phos- 

 Am. Jour. Sci.— Fourth Series, Vol. XXVIII, No. 163.— July, 1909. 



