Most engineers have a sound working knowledge of the handling of materials of different kinds, and of their properties, and make use of these wellknown properties. If, however, the engineer attempts to explain any of these properties he frequently finds that his training has not equipped him with an acceptable explanation.

In recent years much work has been done towards explaining these properties, but this work is dealt with in the specialist works of chemists, physicists and metallurgists, and is usually not easily available for the engineer, involving as it does a great deal of reading and investigation.