Hippalos and Monsoon

"The Whole round of the voyage from Kane and Endaimon Arabia, which we have just described, used to be performed in small vessels which kept close to shore and followed its windings , but Hippalos was the pilot who first , by observing the bearings of the ports and the configuration of the sea, discovered the direct course across the ocean; whence as, at the season when our own Etesians are blowing , a periodical wind from the ocean likewise blows in the Indian sea, this wind, which is the south-west, is, it seems, called in these seas Hippalos (after the name of the pilot who first discovered the passage by means of it).

From the time of this discovery to the present day, merchants who sail for India either from Kane or as others do from Aromata, if Limurike be their destination, must often change their track, but if they are bound for Borugaza, or Skythia they are not retarded for more than three days, after which, committing themselves to the monsoon which blows right in the direction of their course, they stand far out to sea, leaving all the gulfs we have mentioned in the distance."

NOTES
1. The account given above is taken from M'Crindle's translation of the "Periplus Maris Erythraei' (The Periplus of the Erythraean Sea), which describes the travel and trade in the Indian ocean by an anonymous merchant of the first century.
2. Hippalos was an ancient Greek sailor who, believing that there was a seasonal wind which blew between the Arabian Peninsula and Asia, managed to sail to Asia. It is generally accepted that Hippalos made his discovery in the first centuary A.D.