Tables 456-458. 



371 



PERMEABILITY OF SOME OF THE SPECIM.NS IN TACLE 445. 



TABLE 456. 



This table gives the induction and the permeability for diflFerent values of the magnetizing force of some of the sped 

 mens in Table 44S' The specimen numbers refer to the same table. The numbers in this table have been takec 

 from the i Lirves given by Dr. Hopkinson, and may therefore be slightly in error ; they are the mean values foi 

 rising and falling magnetizations. 



Tibles.'isT.g, JS3-6 give the results of some experiments by Du Bois,* on the magnetic properties of iron, nickel, and 

 cobalt under strong magnetizing forces. The experiments were made on ovoids of the metals 18 centimeters long 

 and 0.6 centimeters diameter. The specimens were as follows: (i) Soft Swedish iron carefully annealed and 

 having a density 7 82. (2) Hard English cast steel yellow tempered at 230° C. ; density 7.78. (3) Hard drawn 

 best nickel containing qg % Ni with some SiOj and traces of Fe and Cu ; density 8.82. (4) Cast cobalt giving 

 the following composition on analysis: Co =: 93.1, Ni=: 5.8, Fe = o.8, Cu = o.2, Si:=o. i, and € = 0.3. The speci- 

 men was very brittle and broke in the lathe, and hence contained a surfaced joint held together by clamps during 

 the experiment. Referring to th? columns, H , B, an \ ft. have the same meaning as in the other tables, 5^ is the 

 magnetic moment per gram, and /the magnetic moment per cubic centimeter. jV and .S" are taken from the 

 curves published by Du Boia ; the others have been calculated using the densities given. 



MAGNETIC PROPERTIES OF SOFT IRON AT 0° AND 100° C. 



TABLE 457. 



MAGNETIC PROPERTIES OF STEEL AT 0° AND 100° C. 



TABLE 458. 



* " Phil. Mac." n series, vol. xxix. 



t The results in this and the other tables for forces above i2oo were not obtained from the ovoids above referred 

 to, but from a small piece of the metal provided with a polished mirror surface and placed, with its polished face nor- 

 tnal to the lines of force, between the poles of a powerful electromagnet. The induction was then inferred from 

 the rotation of the plane of a polariied ray of red light reflected normally from the surface. (See Kerr's " Constants." 

 P.331-) 



Smithsonian Tablc*. 



