with all exploration routes between 1648 and 1867 and a map with sea-temperatures in the Greenland Sea and the Norwegian Sea as observed by the German expedition, and again two maps of the German expedition in Ergänzungsheft 28. In 1874 he again published an overview map of the Arctic at a scale of 1:16,000,000, this time with exploration routes from 1616 to the end of 1874, complemented by the new meteorological weather stations. Strangely enough, the route of the 1868 German expedition is not engraved in the image. Petermann still believed however, that Greenland stretched far into the Polar region. The text in the map reads: 'Unerforscht, wahrscheinlich Land oder Inseln (Petermann's Hypothese)' [unexplored, probably land or islands (Petermann's hypothesis)]. In the case of the polar regions, Petermann's point of view deviated from most contemporary views. While many, especially the Americans and British, saw a possible passage in the Northwest, where they expected to find a passage after rounding Greenland, Petermann thought this not a viable option. But this did not prevent him from publishing many reports and maps of the American and British explorations in this area, sometimes translated from the journal of the Royal Geographical Society and other geographical societies. Though he was right in hypothesizing that the warm Gulf Stream complemented the cold Labrador Stream and that the warm stream extended far north of Spitsbergen and Nova Zembla, his thesis that it warmed the Arctic needed serious revision. Although he thought it to be a deep stream, he overestimated the effect of the warmth from that depth on surface ice east of Svalbard. On the other hand, he was wrong about the extension of Greenland. He wrote: "... but such an enormous glacier like the one named after Von Humboldt points at extensive eternal snow and glacier regions and this speaks for an extension of Greenland to the North ..." His view may have been reinforced by some explorers who sighted land at higher latitudes than the tip of Greenland. While Petermann was honored in 1876 by the American Geographical Society, during the last of 3 weeks visiting the US, Dr. Isaac I. Hayes disputed the hypothesis of Petermann's land tongue stretching from Greenland to the Bering Sea, though he agreed that the Arctic Ocean would possibly have open water. The Northwest Passage indeed proved to be challenging. Only in 1904 did Roald Amundsen achieve its navigation.