The Darent is a Kentish tributary of the River Thames and takes the waters of the River Cray as a tributary in the tidal portion of the Darent near Crayford. 'Darenth' is frequently found as the spelling of the river's name in older books and maps, Bartholomew's Canals and River of England being one example. Bartholomew's Gazetteer (1954) demonstrates that Darent means "clear water", a result of it springing from and running through chalk. The purity of the water was a major factor in the development of paper and pharmaceuticals in the area.