University of Bristol - Historical Photographs of China reference number: NA16-082. Image from an album in The National Archives referenced as ‘HONG KONG 3. Views of Hong Kong from the 1860s to the 1920s' (CO 1069-446). According to the Hong Kong Observatory, the highest record of daily rainfall ever recorded in Hong Kong, is 534.1 millimetres - the 19th July 1926 rainstorm. See https://www.hko.gov.hk/en/blog/00000135.htm. Glenealy Ravine was a valley between Government Hill and Pedder's Hill. It was also known as Elliot's Vale and is now a road (己連拿利). See NA18-06 and NA18-07.
Black and white photograph
The National Archives, London