A superb chart detailing the Monsoon from the North East in the Indian Ocean. It includes the ancient routes of trading to the Middle East and India, Ocean currents and wind directions. It was published by Robert Sayer (1725-94) in the ‘East India Pilot’ from 1778. This issue is a French licensed edition engraved by Jean Lattre and published by Sayer and Bennett. Indeed if may well be the original as the author of the map is the noted Frenchman Vicomte Grenier. Not in Shirley but refer to M.Say 3a no. 27.