146 N. D.C. Hodges—Method of Determining the Dr. 
both bars above the line of dip, then both below or in a position 
nearly 180° from the first, finally moving them so as to present 
the other side to the needle in each of the first two positions. 
The first series of observations were made to see how con- 
stant the readings would be and how sensitive the method. 
They were all taken within twenty-four hours. After two of 
them the testing needle was changed from hanging horizontally 
to hanging at an angle of 45°. This was done to see if the 
poles at the outer ends of the bars had any influence. If the 
mean in the beginning. The bars seemed nearly free of per- 
lst Series. 
A, ie 17-2 16-7 15-6 14-5 13-5 13) 
B, T1: 70°% 70°6 71°6 72-7 73°38 142 
C, 10°3 70-7 71: 718 13° 14:4 4 
D, 16°2 15°9 165 159 74-4 73:1 13° 
Average, 73°6 73°6 13°T 73°T 13°T 13-7 73°6 
The second series shows the effect of magnetizing one of the 
bars. The first three were taken in the morning, the last two 
in the afternoon, after the magnetizing. While the latter were 
being made, the magnetic state of the iron was rapidly chang 
ing, as the corresponding readings placed opposite one another 
show, and rendered any accuracy impossible. 
2d Series. 
10-2 10°5 69-9 87-5 84.5 
7 16-4 16-1 BTS 60°8 
16-9 11-2 16-4 P 
10°3 701 705 19°5 80° 
13°6 13-6 73-2 14:1 13°28. 
the magnetism by rapping the bars with a hammer 
determination. The separate readings ees the value of 
3d Series. 
84-3 83-2 80-9 80-2 80°3 
0-2 62°5 65-4 66-4 66°8 
69°6 70-1 726 73° 12°4 
81° 793 163 152 16°T 
13°9 13°38 13°38 13-7 T1417 
