I have been asked by Professor Gregory to examine and describe two pebbles which he has collected from the pre-glacial gravel of Little Hayes, in the Crouch Valley, South-East Essex. Examined in thin section under the microscope, one of these pebbles agrees very well with the typical chert of Arngrove (Bucks) and Studley (Oxon) in size of spicules, their mineralization, their number in a given field, and the proportion of angular sand-grains.