AMONG the tercentenary celebrations of Newton's birthday was a meeting of the London and Home Counties Branch of the Institute of Physics held on December 9. The meeting was addressed by Dr. H. Buckley, of the National Physical Laboratory, and very appropriately was held in the Royal Institution, where a few days previously the Royal Society celebrations had taken place. Dr. Buckley's theme was “Some Historical Aspects of Newton's Work”. He reviewed Newton's life in its relation to his scientific work, bringing out his interest in experimental studies and recounting the development of the papers presented, generally as the result of invitation, to the Royal Society. Speaking of the “Opticks”, Dr. Buckley pointed out that, as in the “Principia”, Newton develops the subject by the formal method of propositions, each followed by proofs, but whereas in the “Principia” the proofs are mathematical, in the “Opticks” they are accurate and clear descriptions of experiments. An informative account of the fate of the various editions of the “Principia” was given. As is well known, the first edition was produced at Halley's expense. It appeared in July 1687 as one small quarto volume of 500 pages bound in calf and was sold at 10s. to 12s. a copy. This sold quickly and by 1691 was difficult to obtain. A second edition appeared in 1713, produced with the assistance of Roger Cotes, the young Plumerian professor of astronomy at Cambridge ; 750 copies were printed, of which 250 were sent to France and Holland. It sold in England at 15s. a copy, and up to 21s. bound in calf. Bentley, then master of Trinity College, Cambridge, bore the cost of publication Cotes received twelve complimentary copies, but probably he refused all other recompense. A third edition appeared in 1726, but this contained only minor alterations ; it was edited by Henry Pember-ton, who received. £200 from Newton for his work. Pemberton is also reputed to have received £3,000 for his “A View of Sir Isaac Newton's Philosophy”, which was published by subscription ; the subscribers numbered some 2,400, including peers of the realm, most of the bishops, and other notables including Alexander Pope and Edward Gibbon, a remarkable tribute to the esteem in which Newton was held. Collected editions of Newton's work were published in Lausanne and Geneva in 1744 in three volumes, and in London during 1779-85, though neither is complete. It is to be hoped that steps will be taken to produce a complete edition of the works of Britain's most distinguished natural philosopher.