A 2¼ square film negative. The Type 12 frigate Yarmouth (1959) in No. 2 dry dock in Rosyth Dockyard. A very close view of a port propeller blade edge showing the Agouti system which involves a row of very small holes in the outer edge of each propeller blade. The Agouti system (also known as a nightshirt propeller silencer) is a method of reducing propeller noise from cavitation. The system consists of drilling holes along the leading edge of the propeller, which are supplied with pressurized air. The air pumped through these holes ventilate the vapour layer reducing noise. The photograph is taken from the bottom of the dock.