highlighted by coloring. The 1857 issue of PGM uses the same copperplate, but with both routes highlighted and another title. Sheets 2–14 of Barth's work are route maps on the scale 1:800,000 and 1:1,000,000. In 1855 PGM gives only a summary of the routes of the first half of the total tour, on scale of 1:2,100,000, with added profiles along the borders that do not appear on the detail maps. This was a corrected issue of a map first published in London. In the 1857 issue the map of Touareg-country is a copy, but mainly uncolored. Maps 15 and 16 of Barth's work form a beautifully drafted and colored two-sheet map at a scale of 1:6,000,000 and measures 57 x 85 cm. It depicts the approximate territories of the indigenous tribes. The other maps in the 1857 issue show rather small details of the routes, not beautifully executed, while in the text a plan of Agades is inserted (I do not know if it exists in Barth's work). All in all, there is little overlap, also because the scales used for the different works are mostly different. But the smaller maps are clearly generalizations of the maps in Barth's work. The images in Barth's look sharper, but of course that is also because they are engraved on a larger scale, while all the areas outside the routes, of which nothing or not enough is known are blank. These routes, like many others, were reused in many new maps, such as Barth's route, supplemented with the 1828 routes of René-Auguste Caillé (1799–1838) and Léopold Planet (1850). Invitation for exploring Africa PGM not only reported the findings of explorers but also was proactive in instigating new explorations. Ergänzungsband II of 1863 contains a 10-part map (210x102 cm) of Africa (Karte von Inner-Afrika, that contained all routes of explorers between 1701 and 1863. The most important parts of the map are the blank areas, hoping that they would stimulate explorers to go on expeditions to find out what new things there could be. But it was also a case of marketing PGM, as shown in the memoire that accompanied the map, where Petermann wrote: "The basic idea of our map was to give travellers a sure support for the choice of their routes and guarantee the direction of the explorations, to resolve doubts and stimulate the elucidation of the unknown, and to offer