橫瀾島
In 1917, a numbered signal system was implemented for warning wind conditions in the territory. Different signals were illustrated by different symbols and these were hoisted to indicate the prevailing wind conditions. Initially, the local day signals were displayed at the mast head of the storm signal mast on Blackhead Hill, the Harbour Office, , Green Island signal mast, the flagstaff of the premises of Kowloon Wharf and Godown Company in Kowloon, the flagstaff on the premises of the Standard Oil Company in Lai Chi Kok and the flagstaff near the Field Officer's Quarters at Lyemun. Night signals were displayed at the tower of the Railway Station, on HMS "Tamar" and on the Harbour Office flagstaff. Supplementary signals in the form of a cone were also displayed at Gap Rock, Waglan Island, Stanley, Aberdeen, Shau Kei Wan, Sai Kung, Sha Tau Kok and Tai Po whenever local signals were displayed in the harbour.