TABLE 50.—Relations between the magnetic constants of steel and hardness-Continued. 5. Magnets annealed 10 hours in steam. TABLE 50.-Relations between the magnetic constants of steel and hardness-Continued. Description of magnets.-The rods used in the present experiments differ from the others principally in two respects: in the first place, the maximum of attainable hardness is here of much larger value than in the earlier work; in the second, the degree of longitudinal homogeneity in the glass-hard state (and we may accept this as a fair evidence of structural uniformity throughout the chosen lengths) far surpasses that hitherto obtained. Hardness was carried even as far ag 0° microhm In consequence of the exceptional homogeneity mentioned, we find that the magnetic data are in excellent accordance. 8 = 47.5 (cm2 129 ): With the object of arriving at corroborative results, two pairs of wires of approximately identical degrees of galvanic hardness were selected. These are numbered IX, X, and XI, XII.130 Each of these was broken into magnets such that the dimension-ratios a=10, 20, 30, 40, 50, ob. tained. Certain important physical constants of these 20 magnets, Nos. 21 to 40, have for convenience of reference here been tabulated. The remarks which precede Table 49 apply to Table 51. 131 -- Homogeneity. The criterion for homogeneity was applied in the manner described in p. 121 by carefully examining the rod under experiment with reference to the electrical resistance of the parts between six equidistant points, about 5 centimeters apart. We believe it expedient to 129 The maximum hardness observed with the older material was 8=0.48 Siemens units at 18°, therefore about 8=44.5 (cm3 0° microhm). Cf. Wied. Ann., xi, p. 945, 1880. cm2 150 The rods III.to IX and the magnets Nos. 11 to 20 are discussed in the following chapter. 131 Of course this can only be done approximately. It is not easy to break a glasshard rod accurately at a given point. take the present opportunity of communicating some of these results by way of example. Table 52 contains (columns 2 to 5) the readings immediately taken from a Kohlrausch bridge. The measuring wire of this had been previously calibrated, with due allowance for the small corrections thus resulting. Column 1 shows which of the consecutive lengths (5.07 centimeters) of the steel rod corresponds to the given bridge reading, and the portion of the bridge-wire equivalent to 0.1 Siemens unit. Herefrom the absolute resistances (ohms) of the steel rods per 5.07 centimeters at to are calculated, and the values given in columns 6 to 9. In view of these very satisfactory results, we were justified in simplifying the subsequent work by testing the homogeneity of the four longest magnets only. Magnetic data.-In making the magnetic measurements we used the first position of Gauss. The numerical values of the constants occurring in the formulæ The magnetic results of our experiments, finally, are given in the series forming table (53): TABLE 53.-Relation between the magnetic constants of steel and hardness. |