In 1769 the Scottish geographer Alexander Dalrymple , was translating Spanish letters found in the Philippines in 1762 . He read Luis VÃ ez de Torres ' letter about a passage south of New Guinea . In 1769 the Scottish geographer Alexander Dalrymple , whilst translating some Spanish documents captured in the Philippines in 1762 , had found Luis VÃ ez de Torres ' testimony proving a passage south of New Guinea now known as Torres Strait .