in which leading scientists speak in a programme edited by Professor E. N. da C. Andrade. F.R.s. This week Professor Andrade introduces Professor J. B. S. Haldane , F.R.S., who talks about ' Life at High Pressure,' Professor A. 0. Rankine, F.R.S., whose subject is ' New Methods of Prospecting for Oil: and Sir Percival Hartley. F.R.S.. who explains how the standards of purity and strength are ensured in drugs such as penicillin and those used against diphtheria