46 PROCEEDINGS OP THE AMERICAN ACADEMY 



III. 



CONTllIBUTIONS FROM THE PHYSICAL LABORATORY OF HAR- 

 VARD COLLEGE, UNDER THE DIRECTION OF PROFESSOR JOHN 

 TROWBRIDGE. 



No. XXIIL — THE MAGNETIC MOMENT OF FLEIT- 

 MAN'S NICKEL. 



By J. E. BULLARD. 



Presented June 9, 1880. 



In March, 1879, H. Th. Fleitman published, in the Berichte der 

 Deutschen Chemischen Gesellschaft, No. 5, 1879, p. 454, a paper on 

 nickel, in which he stated that the porosity of nickel was caused by 

 an absorption of carbonic acid in melting, and that the addition of a 

 small portion of magnesium in the metal bath would prevent this 

 absorption. The addition of even one eighth per cent, of magnesium 

 entirely changed the structure of the nickel ; it became very ductile 

 and malleable, took a high polish, and resisted the action of the air. 



As this discovery is of very great importance in the arts, I have 

 endeavored to ascertain whether the magnetic properties of the nickel 

 are changed by the addition of the magnesium which causes such 

 changes in the mechanical properties of the metal. 



The apparatus used was an ordinary telescope and scale, and a 

 magnetometer. A short cylindrical bar of Fleitman's nickel, fully 

 magnetized, was placed before the magnetometer. The method used 

 was the observation of deflections, using the formula M= i r^ J'tan <^. 

 Mis the magnetic moment of the bar; T' is the horizontal intensity 

 of terrestrial magnetism ; r is the distance of the centre of the magnet 

 from the mirror of the magnetometer, in millimeters ; and (p is the de- 

 flection of the mirror caused by the magnet. In the present case, — 



The length of the bar of nickel was 67 mm. and its diameter 6 mm. 



r = 277.5 mm., 



7' (for Cambridge) = 1.65, 



and log tan (f> = 9.6882. 



Hence J/ is found to be 8,600,000. 



