In this ancient and honourable Royal Society we have an association of persons with a common motive, namely to assist the advance of natural knowledge. The chief functions of such a Society are (1) to provide facilities for intercourse, personal and formal; (2) to provide a library—and we have a great library of ever-increasing value ; (3) to provide the means of publication. Records of scientific research are not a readily marketable commodity. They would fare badly if left to the mercy of the ordinary laws of supply and demand. So we meet the cost of publication, and they go out, after some winnowing of chaff from wheat, with our imprimatur. Looking back through the published volumes of our Proceedings and Transactions, you will find papers by Kelvin and other Fellows which may be said without exaggeration to mark epochs in the development of scientific thought.