Foster and Topley worked in the Wealden area and afterwards in Derbyshire. In 1865 the two of them communicated to the Geological Society of London their famous paper On the superficial deposits of the Valley of the Medway, with remarks on the Denudation of the Weald. In this now-classic paper there is a presentation of evidence on how rain and rivers cause erosion and sedimentary deposits.
Foster and Topley's research in Wealden and Derbyshire ultimately resulted in a groundbreaking paper being presented to the Geological Society of London, detailing the formation of surface deposits along the Medway River valley and the process of erosion that created them.