ELECTRODYNAMIC QUALITIES OF METALS. 
75 
The effects of the various operations were measured by the deflections of the image on 
the scale of a reflecting magnetometer, M, the needle of which was on a level with the 
lower end of the bar, and at a distance due magnetic west from its axis of 12 centims. 
The scale of the magnetometer was at a distance of 135 centims. from, the needle. 
231. In these preliminary experiments the bars were under the influence of no 
magnetizing force except that of the vertical component of the earth’s magnetic force 
at Glasgow. In order that the results obtained with the bars of nickel and cobalt 
might be readily compared with those obtained from iron in the same circumstances, 
the experiment was first performed on a bar of tolerably soft iron, of nearly the same 
dimensions as those of the bar of nickel or cobalt experimented on. The actual 
results of a set of these experiments are given in the following tables. Table I. 
contains the results of an experiment on an iron bar 60 centims. long and '8 of a 
centim. in diameter, and Tables II. and HI. the results respectively of two similar 
experiments performed immediately afterwards, one on a bar of wrought nickel and the 
other on a bar of cast cobalt. The total magnetization is reckoned positive when its 
polarity is the same as that produced by the inductive effect of the earth’s magnetic 
force, and negative when its polarity is of the opposite kind. 
Table I.—Iron Bar. Lower end of bar a true South Pole. 
Operations. 
Magnetometer 
readings. 
Differences. 
Total 
magnetization. 
Bar placed in position 
Controlling magnet introduced 
174 lbs. on. 
Zero 463 
f Image off scale 
< in negative 
direction 
769 
675 
-94 
+ 1369 
+1463 
„ off. 
687 
+ 12 
+ 1451 
„ on. 
660 
-27 
+ 1478 
„ off. 
675 
+ 15 
+ 1463 
10 “ ons” and “ offs” 
667 
- 8 
+ 1471 
174 lbs. on. 
649 
-18 
+ 1489 
„ off. 
663 
+ 14 
+ 1475 
259 lbs. on. 
571 
-92 
+ 1567 
„ off . . 
10 “ ons ” and “ offs ” 
597 
+ 26 
+ 1541 
570 
-27 
+ 1568 
259 lbs. on. 
540 
-30 
+ 1598 
„ off. 
569 
+ 29 
+ 1569 
325 lbs. on. 
470 
-99 
+ 1668 
„ off. 
510 
+ 40 
+ 1628 
10 “ ons ” and “ offs ” 
474 
-36 
+1664 
325 lbs. on. 
421 
-53 
+ 1717 
„ off. 
457 
+ 36 
+ 1671 
L 
o 
