SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 240 



case m = 25, and B = 21120, the extra resistance R' had to be made 

 as high as 10,000 ohms in order to keep the throw for the central coil 

 alone from exceeding the length of the scale, yet when the coil nearest 

 to the central one was connected in opposition to it, only a weak de- 

 flection was obtained with no extra resistance in the galvanometer 

 circuit. 



The curves which are shown represent four different rods, all having 

 the largest diameter used, 1.905 cms., but two of these had the same 

 length, the in being = 60, so that for these rods the results are com- 

 bined in one figure. The data for these four rods are as follows: 



TABLE XIX. 



The coils are designated as follows, beginning with the central one : 



No. II. 5-6-7-8-9. 

 No. A. CD-MN-XY. 



No. B. A-B-C-D-E. 

 (No. I) 1-2-3-4. 



The results are given graphically by Figures 23, 24, and 25 in this 

 way: The induction B in the middle part of the rod, as found from 

 reversing the current in the solenoid while only the central coil is in- 

 cluded in the galvanometer circuit, is plotted horizontally ; while the 

 ordinates give the ratio of the corresponding inductions in the parts of 



