MERCATOR, ORTELIUS, AND THEIR SUCCESSORS 123 



Lemos, probably drawn in 1586 or later, which discarded the 

 Mercator conception of the Arctic regions and showed a 

 practicable northern route to the Indies. After the failure of 

 these northern attempts, he concentrated on the African route, 

 and prepared sailing instructions for the second Dutch East 

 Indian voyage of 1598. Four years later he was appointed 

 official cartographer to the Dutch East India Company. He 

 published numerous charts, some of which have not survived, 

 including charts of the Mediterranean on Mercator's pro- 

 jection, and he attempted to solve the problem of the deter- 

 mination of longitude by observing the variation of the com- 

 pass. 



During the seventeenth century the procedure was estab- 

 lished that pilots returning from the east should hand over to 

 the official cartographer their charts with the additions and 

 amendments resulting from their own observations. The 

 cartographer was responsible for collating these, and for pre- 

 paring revised charts for succeeding voyages. A considerable 

 body of such manuscript charts have survived as a witness 

 of Dutch hydrographic activity. The information they con- 

 tained was slow to find its way on to published engraved charts, 

 probably as a matter of policy. Among Plancius' successors as 

 official cartographers were Hessel Gerritsz and the Blaeus, 

 father and son. Gerritsz was in 1622 the draughtsman of a 

 magnificent manuscript map of the Pacific Ocean, largely 

 based on Spanish sources but also incorporating the tracks 

 of the circumnavigators Le Maire and Schouten. Among 

 the charts which he engraved and published was the 'Caert 

 van't landt Eendracht', 1627, which portrayed the coast of 

 western Australia discovered by the Dutch vessel, Eendracht. 

 Willem Jansz Blaeu, who succeeded Gerritz in 1633, was a 

 student of mathematics and astronomy, and the founder of a 

 famous cartographical establishment in Amsterdam, from which 

 issued maps, atlases, wall maps and globes. Willem's tenure of 

 office was short, and in 1638 his son, Joan Wz. Blaeu, succeeded 

 him, and with his experience in his father's office, made a 

 notable contribution to establishing standard charts for the 

 Dutch navigators. With him the great work of his family 

 virtually came to an end, for shortly before his death in 1673, 



