1. Experiments of Hopkinson, Curie, and D. K. Morris.

2. Precautions necessary in magnetic testing. If the temperature of a test-specimen is changed, the specimen must be rendered neutral at the new temperature previous to carrying out the test.

3. The effect of increasing the temperature of a specimen of cast iron from 15° C. to 190° C. is to improve its magnetic quality for moderate values of the magnetising force; from 190° C. to 260° C. the magnetic quality falls off, after which there is a further improvement. Finally the specimen becomes non-magnetic at the critical temperature. These results indicate the presence of a transformation point for carbon alloys of iron in the neighbourhood of 200° C.

4. Steel containing 1·64 per cent, of carbon resembles cast iron in its behaviour. The set-back in magnetic quality takes place at much the same temperature as that which occurs in cast iron, the magnitude of the set-back being much the same for both.

5. Steel containing 0·8 per cent, of carbon exhibits the transformation point, but in a less marked degree. The first maximum point in the susceptibility curve occurs at 180° C, and the first minimum point at 220° C.

6. Low carbon steel containing 0·3 per cent, of carbon shows the transformation point; it is, however, very much less marked than in the case of the steels containing the higher percentages of carbon.

7. The susceptibility-temperature curve of a specimen of soft iron containing 0·06 per cent, of carbon exhibits no turning points in the neighbourhood of 200° C. for fields lying between 2 and 15 c.g.s. units.