104 Barrerr, Brown & HaprieLD—On the Electrical Conductivity and 
The following is an example, taken at random, of the readings obtained in 
going through a complete cycle for one of the specimens; from these readings 
the data necessary for plotting one of the curves given in Plates II].-IX. are 
obtained. 
Taste I.—(Marx 1179 B, Puare VIII.) Chromium-Aluminium Steel. 
Steps. | Magnetising current. | Magnetometer Readings. 
Amperes. Current direct. Current reversed. Current direct. 
0 0-00 OO) | # i1@P7 ) — 20:0 
| Up i 0-07 & OB | + 17-0 — 17-2 
2 0:18 + 2:0 + 9:3 = SP7 
3 0°31 ptics =| §§il ar | GP 
4 0°50 4 iPS) — 18:2 + 18:2 
5 0:94 + 27:0 — 26°6 + 26:3 | 
6 oj) | + 28°3 — 28:2 + 28°8 
U 1°50 + 29:9 J — 30:0 | + 30°2 
Down 6 1:19 + 29:8 - 
5 0:94 + 29°0 — 29:0 4 
| 4 0°50 + 27:0 | — 27:0 
3 0°31 + 25°7 — 25:7 | 
2 0°18 + 23°9 — 24:0 
1 0:07 + 22:0 — 22:0 | 
0 0:00 + 19°7) — 20:0 
Column 1 gives the number of the steps, first up and then down, as already 
explained, p. 102. Column 2 gives the magnetising current round the coil in 
amperes; these numbers multiplied by 30°2—the magnetic force of the coil per 
ampere—give the magnetic force H, acting on the rod in C.G.S. units. Columns 
3, 4, and 5 give the magnetometer readings corresponding to the currents named 
in column 2; the sign + means a reading to the right of zero, and the sign — a 
reading to the left of zero. In columns 3 and 5 the current through the magnetising 
coil is in one direction; in column 4 it is reversed. Referring to fig. 8, the initial 
uprising curve 1 is obtained from the magnetometer readings enclosed within the 
first bracket in column 3; the position of the curve 2 in fig. 8 is obtained from 
the readings in the second bracket in column 3; the current is now reversed, and 
the portion of the curve 3 in fig. 8 is obtained from the first bracket in column 
4, and so on till the cycle is complete. The symmetry of the curves is shown 
by the similarity, for corresponding currents, of the magnetometer readings in 
the first brackets in columns 4 and 5, and the second brackets in columns 3 and 4. 
