THE Pilgrim Trust Lectures, administered jointly by the Royal Society and the U.S. National Academy of Sciences, were inaugurated last December by a notable lecture delivered by Dr. Irving Langmuir in the theatre of the Royal Institution, London. The selection of the lecturer for the second of the series was in the hands of the Royal Society, which decided, most appropriately, to send its president, Sir William Bragg, as the ambassador of science in Great Britain to the United States. Sir William visited the United States during the spring, and on April 24, in the course of the annual meeting at Washington of the National Academy of Sciences, delivered the second Pilgrim Trust Lecture, which appears on p. 21 of this issue of NATURE. The effect of science upon social conditions formed the theme of Sir William's address, which he illustrated by dipping into the history of the Royal Society Starting as a body of ‘virtuosi’ who met for discussion and experiment about the middle of the seventeenth century, the Royal Society early became concerned in problems of interest to a wider circle and to the State. Inquiries submitted to correspondents, their reports, and papers read before the Society, illustrate the effects of science upon society and conversely, of the circumstances of the times upon scientific investigations. Sir William leads up to an eloquent plea for the earnest consideration of current affairs in the spirit of science, which links up with the efforts of the Division for Social and International Relations of Science of the British Association; the Manchester meeting of the latter referred to on p. 1 of this issue deals specifically with some social aspects of scientific research, while Sir William points the moral on the wider issue.