Letter Book of the Royal Society: 'original' copies Contains copies of letters received by the Society on diverse areas of natural philosophy. These are copies of original documents, many of which can be found in the Early Letters collection, though not all items in the letter books have a corresponding original in the Royal Society collections. Originals were submitted to be read at meetings of the Society and published in its journal Philosophical Transactions of the Royal Society. They were copied into the letter book for security and to establish a record of priority. The numbering of the volumes and their chronological range is slightly eccentric. Volumes numbered 1-18 are letters of 1662-1727;within this group, Volume 11 has been extended into two volumes. Volume 17 was created in order to leave a gap in the series for retrospective copying of original papers. The succeeding Volumes 19-26 overlap in time, giving correspondence for the years 1720-1740. There are also five supplementary volumes providing fair copies of letters omitted from the main run; these are labelled A-B, B-C, D-G, G-H and H-S, the letters being arranged in order of author. 1661-1740