Plate from \Theoretical considerations on () the drift deposits containing the remains of extinct mammalia and flint implements\", 1864. Phil. Trans Roy Soc 154. Jospeph Prestwich was a geologist specialising in hydrogeology, famous for his work confirming the antiquity of man. In 1859 he followed a lead by Hugh Falconer that it was worth checking the claims of Boucher de Perthes that the Somme gravels contained human artefacts in place with an extinct megafauna. With friend John Evans he found and photographed handaxes in situ in the gravels and presented his detailed work to the Royal Society. The work fairly rapidly won acceptance (though the details and exact dates of the tools long remained unknown). In 1863 the influential geologist Sir Charles Lyell published his book on Human Antiquity supporting the case for a long human chronology. This is the definitive early remains site map."