|In 1569, Gerard Mercator made three prints of his famous map of the world, using the "Mercator projection" he invented. The formulas for this projection use logarithms, but logarithms weren't invented until at least 1588 (when a Swiss clockmaker named Burgi knew about them, but did not publish), or maybe 1614, when Napier published his Minifici Logarithmorum Canonis Descriptio. I wondered how Mercator made his map without logarithms. In 2000 or 2001 my friend Joel Spruck and I tried to see the copy of this map at the National Museum in Paris, but we were unsuccessful--they claimed they didn't have the map after all. (I still don't know if the Paris copy really exists.) The other two copies are in Hamburg and Rotterdam. The copy in Rotterdam has been cut up and made into a (very large) book. My friend Freek Wiedijk and I went, by appointment, to see it. One of the curators of the museum met us and turned the pages for us. We weren't allowed to touch the map, but we were allowed to photograph it. Here are the photographs I took.