Contemporary vellum with 4 strings. With fine half-page engraving on half-title, woodcut vignette on title-page, 6 folding engraved tables and several woodcut diagrams in the text. First edition. - 'The tables are the first logarithmical tables in a Dutch navigation book. The tables are probably computed and enlarged by Adriaen Vlacq and based on those of John Napier and Henry Briggs' Around 1680, Abraham de Graaf also managed to combine his private school with the position of examiner of helmsmen at the VOC and the WIC. And apparently the blood was already crawling where it couldn't go. After his appointment as examiner by the VOC, he received an instruction in 1681 in which it was stipulated that anyone who wished to do so could take the examination with him, regardless of whether the person concerned had learned the art from the Count or from someone else. De Graaf would not be allowed to favour anyone or make a distinction between candidates who had taken lessons with himself or with others, it was also laid down in the instruction. And to put an end to any remaining ambiguity: he was also not allowed to accept gifts or oblige mates to buy goods from himself and he had to continue to behave as 'befits an honest and faithful examiner'. Nevertheless, eleven years later, De Graaf was emphatically reminded of his duties.36. After his death in 1714, the instruction of his successor was significantly expanded with one stipulation: an examiner of the mates was no longer allowed to hold a private school at the same time.