At the close of our last Session, I undertook to call the attention of the Fellows at the commencement of the present to the history of the Eoyal Society, taking as my theme the completion of its hundredth anniversary. Circumstances have accidentally delayed for a month or two the fulfilment of that engagement; but I now proceed, to the best of my power, to discharge it. It is a very wide theme, and it will at once occur to you that a review of the topics which have engaged the attention of the Society during that period, rightly performed, would be equally beyond my ability and your patience. I should have to speak an encyclopaedia, in many volumes. I can, however, but attempt some desultory and fragmentary reflections, which may not be devoid of interest, on “the Foundation and the Founders of the Eoyal Society of Edinburgh,” as they appear to us in retrospect through a vista of a hundred years.