Although Jurong's geography was documented on a few maps and records following Singapore's founding in 1819, the area only became clearer to the British in an 1828 geographical survey of the island by Lieutenant Philip Jackson. In a map that was drawn after the survey, the lieutenant clearly describes most of Jurong's natural geography with the two rivers of Jurong, Sungei Jurong and Sungei Pandan, marked on the map. He also noted down several islands which have since ceased to exist. Such islands include, Pulau Ayer Chawan, Pulau Butun, Pulau Pese (Pulau Pesek), Pulau Sakra and Pulau Saraya (Pulau Seraya), all of which have since merged to form Jurong Island. Current geographical landmarks such as Pulau Damar Laut and the strait of Selat Sembilan (now Selat Jurong) have also been included on the map.