354 MR. 0. CHREE ON THE EFFECTS OF PRESSURE 
performed. No pressure or tapping was applied to the rod throughout these observa¬ 
tions. The current was always in the direction making the end A the north pole. 
The results, as recorded in Table V., are deduced from the scale readino-s taken 
(l) with the rod in its place inside the coil immediately after the break of the 
current, (2) with the rod removed to a distance. In general, two observations were 
taken for each strength of field. The mean of the two observations is the 3/ of 
the Table. By Ip is meant the strength of the field due to the current just broken, 
and by /c/ the ratio of to <§. The mode of variation of 3/ with Ip is shown in 
curve a, fig. 10 ; while the mode of variation of k{, which is subsequently termed the 
residual susceptihilitij, is shown in curve a, fig. 11. 
Table V. 
ATi '. 
3f. 
/ 
^'l • 
1-7 
•22 
•13 
14-1 
12-9 
•91 
2-6 
•29 
•11 
10-1 
15-8 
•98 
.3-5 
•66 
•16 
18-0 
21-4 
1-20 
4-4 
•95 
•22 
22-3 
27-5 
1-23 
5-0 
1-3 
•25 
25-0 
28-5 
1-14 
5-6 
2-0 
•36 
27^3 
31-5 
1-15 
6-0 
2-4 
•40 
38-0 
43-0 
113 
7-0 
3-8 
•55 
45-4 
50-1 
1-10 
9-4 
6-6 
•70 
54-6 
56-4 
1-03 
11-5 
9T 
•79 
70-4 
61-9 
•88 
12-2 
10-2 
•84 
79-4 
63-8 
•80 
§ 33. In continuation of these experiments a much more elaborate set of obser¬ 
vations were taken, with the object of determining whether the amount of the 
residual magnetisation or its properties depended on the treatment of the rod during 
the flow or break of the current. In one set of experiments, spoken of in future as 
the L type, no pressure at all was applied during the flow of the current. In a 
second set, the M type, six cycles of pressure “ on ” and “ ofl“” were applied, the current 
being broken when pressure was “ ofl'.” In a third set, the N type, a pressure was 
applied after six pressure cycles, the current being broken when pressure was “ on.” 
In these, as in all the other experiments, the rod was introduced into the coil after 
the scale reading showed that the current had become steady. The experiments of 
the several types were not conducted separately, but on the following plan. Starting 
with a certain number of storage cells and a certain resistance in circuit, complete 
observations were made for the corresponding held wdth each of the three types 
in the order L, M, N, say. Then with a greater number of cells, or a reduced 
resistance, observations were taken for the next higher field, in the order M, N, L, 
and so on, in cyclic order. Care in fact was taken that the experiments of any given 
type shoukl not unduly often be either the first experiment of the day or the first 
