MAGNETIC PERMEABILITY OF IKON, STEEL AND NICKEL 45 



the iron, and hence did not give a normal curve for high magnetizing- 

 powers. However, I have collected in Table VIII some of the results 

 of these experiments; but I have many more which are not worked 

 up yet. 



In the following Tables Q= -^ has been measured as previously 



described. It is evident that if, instead of reversing the current, we 

 simply break it, we shall obtain a deflection due to the temporary mag- 

 netism alone. In this manner the temporary magnetism has been 

 measured; and on subtracting this from Q, we can obtain the permanent 

 magnetism. 



The following abbreviations are made use of in the Tables, the other 

 quantities being the same as previously described. 



C.T.G. Number of coils of tangent-galvanometer used. 

 D.T.G. Deflection of tangent-galvanometer. 

 D.C. Deflection from coil G. 

 D.F. Deflection from helix F on reversing the current. 



Q. Magnetic field in interior of bar (total). 

 D.B. Deflection from F on breaking current. 



T. Magnetic field of bar due to temporary magnetism. 

 P. Magnetic field of bar due to permanent magnetism. 

 n. Number of coils in helix F. 



Each observation given is almost always the mean of several. D.T.G. 

 is the mean of four readings, two before and two after the observations 

 on the magnetism; D.C. is the mean of from four to ten readings; D.F. 

 mean of three; D.B. mean of two, except in Table I, where the deflec- 

 tion was read only once. In all these Tables the column containing 

 the temporary magnetism T can only be accepted as approximate, the 

 experiments having been made more to determine Q than T. 



The value of n was generally varied by coiling a wire more or less 

 around the ring, but leaving its length the same. 



The change in the value of D.C. is due to the change in the resist- 

 ance of the galvanometer from change of temperature, copper wire 

 increasing in resistance about 1 per cent for every 2 -60. rise. In 

 Table I the temperature first increased slowly, and then, after remain- 

 ing stationary for a while, fell very fast. 



