The Science of Materials
2: The Fascination of Imperfect Crystals by E. W. J. MITCHELL , Professor of Physics in the University of Reading Last week Professor Mitchell dealt with the ways in which atoms are built up into familiar materials. This time he describes the research that explained why sometimes a material is an insulator and at others a conductor. The power to make a material with just the right properties is of great technical importance-one example being the revolution brought about by the transistor. not only in social habits, but in industry as well.