This rarely-seen little book provides a detailed account of the construction of Fernworthy Dam within the geographical context of Dartmoor (Devon). It also outlines the technical challenges that faced the civil engineers responsible for this project. The reservoir enclosed by the dam is the major water supply for the Torbay area. The account itself is a much-augmented version based on a lecture presented by the two authors to the Institution of Civil Engineers in London on 12th December 1946.