After two short seasons spent in investigating the high terrace of the lower Thames, it was considered desirable to examine the gravel of a tributary, in order to equate if possible the various deposits in the two valleys, and to confirm or correct the sequence deduced from former excavatións at home and abroad. Two sites near Rickmansworth, at and just below the junction of the Gade and Colne rivers, have been known for years as productive of palaeoliths, and every facility was readily afforded for examining the gravel in pits at Croxley Green and Mill End by the respective owners, Gonville and Caius College, Cambridge, and Lord Rendlesham, and the lessees, the RickmansworthGravel Co., Ltd., and Messrs. Horwood Bros. Leave of absence was granted by the Trustees of the British Museum, and nine days were devoted to the work in October, the means being provided from a fund under the control of our Vice-President, Sir Hercules Read, Keeper of the Department concerned. Assistance from the geological side was given unofficially by Mr. Dewey, of H.M. Geological Survey, who has read through the paper in manuscript, and contributes an appendix dealing with some of the geological problems involved.
