This week. Professor E. N. da C. Andrade, F.R.S., introduces: 'Electron Diffraction and the Electron Microscope,' by G. I. Finch , M.B.E., F.R.S., Professor of Applied Physical Chemistry at the Imperial College of Science; and 'Something New about Fossils,' by D. M. S. Watson , F.R.S., Professor of Zoology. University of London