THAT part of the county of Middlesex lying to the west of the Finchley and Barnet Ridge has an area of about 160 square miles and is drained by four main streams, the Colne, the Ash, the Crane and the Brent and their tributaries, all of which flow to the Thames above London. In the post-war years the population and industries of this district increased and developed so rapidly that the twenty or more local authorities acting individually were unable to keep pace with the requirements, particularly in respect of sewerage and sewage disposal. Mr. David Mowat Watson has given the history of the scheme which was adopted to deal with this problem, and a description of the works and their design and construction (J. Inst. Civ. Eng., April), for which he has just been awarded the Telford Gold Medal of the Institution of Civil Engineers.