The most important part of the paper has to do with the behaviour of certain iron and nickel tubes, considerably shorter and narrower than those discussed in Part I. Two iron bars, A and B (A being twice the length of B), and a nickel bar, B, were bored out by successive stages, so as to give three series of tubes of increasing bore. Each tube was subjected to four distinct experiments. These were—

1. Measurements in various magnetic fields of the corresponding changes of volume of bore.

2. Measurements in the same fields of changes of length.

3. Measurements in the same fields of changes of volume of the material of the tube.

4. Measurements in the same fields of apparent external changes of volume, the tube being plugged and treated as a bar.