earth inductor in the same circuit thrown over two right angles). There was a certain amount of permanent magnetism, and the result is indicated in the following table and plotted in a curve (fig. 2). The field intensity was not very different at different depths in the channel; it varied from 1730 cgs. near the rim to 1830 near the winding, when 110 volts were applied.
| Exciting current in amperes | 0.0 | 0.34 | 0.67 | 1.32 | 1.92 | 2.52 | 3.18 | 3.80 |
| Field in cgs. lines per sq. centim. | 92 | 255 | 490 | 980 | 1310 | 1530 | 1670 | 1800 |
The maximum current was commonly used for purposes of excitation; and sometimes for a short time this current was doubled, by the application of 220 volts.
By the 8th June, 1892, this iron mass, weighing 14 cwt., had been mounted on the vertical shaft of the whirling machine, in place of the steel disks, and a spin was taken, with the optical frame in good action, and one half of the beam of light going three times round in the channel of the iron.
The shaft, however, was rather too weak to carry the weight, and exhibited a tendency to bend, which prevented the attainment of high speed. Moreover, the step bearing on which the shaft rested (as described in the previous paper, the shaft was supported on a hard steel pivot resting on another steel surface inside an oil
