Though Petermanns name appears on hundreds of maps, Wagner suggests he stopped drafting maps himself after 1862. The report concerning the
Nordenskiöld voyage to the
Lena River, and the maps of the United States and Australia, suggest this may not be true. Perhaps he no longer designed, constructed and drafted the maps, as he had with the Barth maps, but he most likely continued to play a role in the conception and design of the maps, especially those in his fields of interest. Petermann was very well aware that even topographic maps were not yet a true representation of reality (this is illustrated by the depiction of the
Liparian Isles, which were not securely situated until Darondeau's French survey in 1858), let alone medium- and small-scale maps of the interior of continents and the polar regions. One could still hardly speak of dense topographic, orographic and hydrological information. Though the maps in the Stieler looked dense with information, they were mainly filled out with information where space in the image allowed, and the cartographers had little choice what to depict by the lack of known phenomena. The density of information did not indicate how thoroughly an area had been explored, for the cartographers selected their data and drafted the maps in such a way as to give a balanced image as possible. As Petermann put it in 1866: "In fact, our cartographic knowledge of the territories of the earth is far less than is generally supposed. ... [In the maps,] even the African and Australian terrae incognitae shrink more and more, and there remain [only] a few blank spots, maybe 'wild territories', where there is 'nothing'. In reality everything we see on our maps is just the first step, the beginning of a more accurate knowledge of the earth’s surface." The results of the exploratory expeditions cried out for presentation in map form, and PGM published exploration results as quickly and accurately as possible. Petermann had all results he received from explorers checked against the considerable information and maps available in the Perthes Institute. This fund of knowledge grew to be so large that the Institute soon had a large library of manuscripts, books, atlases, and maps at its disposal that could vie with any university or society collection. In the 1980s it was thought that the Perthes-archives contained 180,000 printed maps and around 2,800 atlases. In the 1990s the estimate was 1,000 m of archive, some 400,000 maps (including manuscripts), and some 120,000 geographical works. All collections (currently estimated at 185,000 sheets of maps, 120,000 geographical works, and 800 m of archives) were acquired in 2003 by the Free State of
Thüringen and deposited with the library of the
University of Erfurt in its research center in
Gotha. But the maps went beyond a simple presentation of the itinerary by also describing the area explored with all knowledge available and pointing out gaps that remained to be filled in the current knowledge. So the impact was reciprocal. Moreover, Petermann gave directions to explorers in exchange for which he was allowed to publish their results as soon as possible.
Richardson's African expedition The influence Petermann tried to wield, even as a young man, can best be illustrated by his interference, together with Bunsen and Ritter, on behalf of
Heinrich Barth, who wished to take part in the Richardson expedition. He later also persuaded the English government to send
Eduard Vogel after them for scientific research and astronomical observations. Petermann published the results under the title
Account of the expedition to Central-Africa. When first Barth and later Vogel failed to return at the expected time Germany frantically tried to discover their fate, much as Britain had with Franklin in the Arctic area. This led to many new German expeditions to Africa (by
Theodor von Heuglin,
Hermann Steudner, Theodor Kinzelbach,
Karl Moritz von Beurmann,
Gerhard Rohlfs,
Karl Mauch and others), most financed by gifts due largely to Petermann's agitating actions and publications. Many found their death in Africa as shown in the map with the subtitle
Four martyrs of German science in Inner-Africa shows, i.c. Overweg, Vogel, Beurmann and Steudner. Petermann first drafted maps of Barth & Overweg's routes for the journal of the German Geographical Society and followed these up with maps in PGM in 1855, 1857, and 1859. These were later worked into the maps for Barth's voluminous work on his African voyage of 1850–55. The route maps were used in new maps up to 1893. When we compare the maps in Barth's work and in PGM we may get an idea of how the information was turned into images. The first map in Barth's work gives an overview of his routes. The routes of
Livingstone have already been engraved, but have not been 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 a means for friends at home to follow their moves and to judge the value of their labour. This by creating a cartographic representation of the least known central regions of Africa utilizing all material at hand as completely as possible, to display the range of our contemporary knowledge as well as the way this knowledge is acquired and the degree of its reliability."
Arctic explorations Petermann spent a lot of time on the active promotion of his exploratory missions, especially the polar regions. For this he wrote more articles than for any of his other ventures. Up to 1871 he published seventeen maps of the
Arctic and
Antarctic in the regular issues and eight in the 'supplement' issues. He began publishing notices on the geography and exploration of the polar regions in PGM 38, 1871 (
Geographie und Erforschung der Polar-Regionen started in 1865 and nos. 51–135 appeared in PGM volumes 16, 1871 to 23, 1878), and from that time onwards 195 maps covered the polar regions, but none appeared in the supplements of that period. He actually started to push his interest in this subject in the 1865 issue of PGM and with the publication of supplement 16 (Ergänzungsband IV) in 1865. In the PGM-issue he recites the correspondence he has with the Royal Geographical Society (RGS) concerning the proposal of capt.
Sherard Osborn (1822–1875) to send another English expedition to the North pole starting from Baffin Bay. In several articles he tries to persuade the RGS to support his plan to start the expedition from
Spitsbergen and use steamships instead of sledges for transport. In one article he stresses his love for Arctic expeditions by reminiscing: "Who, like us, e.g. has attended the accounts of one capt. Inglefield (
Edward Augustus Inglefield (1820–1894)) during the session of the Royal Geographical Society of London on 22 November 1852, would be persuaded to know that the natural beauty of the Arctic regions cannot be surpassed by any other in the world." Though the accompanying map shows his theory concerning an extended Greenland he doesn't write about this, but mainly about his errouneous theory concerning the behavior of the Gulf Stream. Supplement IV gives an overview of the knowledge of the area around Spitsbergen and the central Arctic. It contains articles by Petermann, R. Werner, N. Dunér and
A.E. Nordenskiöld, Dr. Malmgrén,
Barto von Löwenigh, and G. Jäger, and is accompanied by three maps. Petermann published this supplement issue to encourage people and institutes to support German efforts to explore the central Arctic. The first map, scale 1:40,000,000 covers both the Arctic and Antarctica, with the routes of the explorers from
Cook to 1861. He measures the unexplored area in the Arctic as 140,000 German square miles (approximately 7,700,000 km2), comparing it to Australia's total of 138,000. The unexplored Antarctic he calculates as 396,000 German square miles (approximately 21,800,000 km2). Petermann uses the map specifically to show the benefits of using ships for exploration, rather than the sledges usually used by the Americans and the British. He must have been convinced that the central Arctic contained vast expanses of open water and land, the latter presumably extensions of Greenland and Spitsbergen. Though the routes in the Antarctic map have been engraved, they are not highlighted in color. Instead Petermann has colored the polygons that encompass the areas covered by the several explorers. This highlights the unexplored area clearly, even though it is blank. But Petermann is definitely more interested in having the Germans explore the Arctic than the Antarctic, presumably because the costs of an Arctic expedition can be met more easily than those of an Antarctic one. The more detailed map of Spitsbergen not only shows the Swedish surveys of 1861 to 1864, but also the presence of coal fields, coastal areas with driftwood, and areas where reindeer can normally be found. Petermann's last map is in the modified polar projection first proposed by G. Jäger of
Vienna. Jäger had developed this projection specifically to facilitate the palaeontological analysis of the inventory of animal life in the Arctic area. Petermann thought this the best projection for planning the laying of telegraph lines.
North-East passage He not only promoted explorations, but also actively collected funds to realize them, and gave an account of the receipts and expenditures in several issues of PGM. In 1865,
Otto Volger of the FDH (
Freies Deutsches Hochstift für Wissenschaft, Künste und allgemeine Bildung, founded in 1859) organised the 'Allgemeine Deutsche Versammlung von Freunden der Erdkunde' (General German Assembly of Friends of Geography). During this two-day meeting
Georg von Neumayer stressed the fact that Germany needed a German maritime institute to be independent of other nations. One of the programmed issues to be discussed was the issue of guidelines for the use of a homogeneous meteorological logbook for the German merchant navy. In later years the maps in PGM made much use of the data thus gathered. Petermann jealously reported on the marine surveys in Britain and America, which were realized with governmental support, and he dearly wished such was possible in other nations, especially Germany. Furthermore, he pointed out that Germany had much to gain by exploring the Arctic region, especially the
Northeast Passage, since the English and Americans were concentrating on the
Northwest Passage. Though he even tried to get
Bismarck involved in an
Arctic exploration project, it was shelved for some time because of the
Austro-Prussian War and the consequent expansion of the
Prussian realm. In PGM that same year, he again turned to the FDH for support. In 1868 Petermann roused so much support for his idea in the German public that his Arctic expedition actually took place. He proposed to follow a course east of Greenland, for he and other geographers were convinced that Greenland stretched much farther North than was known in that time. Though
Ferdinand von Wrangel started a four-year-long expedition in 1820 to find possible land north of
Cape Shelagskiy and could not find any land, he noted a
Chukchi chief saying: "One might in a clear summer's day descry snow-covered mountains at a great distance to the north." Heinrich Berghaus, Petermann's teacher, included this information in the right hand corner on his isotherm map of 1838 for his
Physikalische Atlas with the text 'possible polar land' [Wahrscheinliches Polar-Land]. So it might be that Petermann based his views on this information. He published the same map of the Arctic and Antarctic as in 1865, but now with Greenland stretching over the Arctic and ending in
Wrangel Island close to the
Bering Strait. It shows the possible route of the German expedition. The Antarctic map now uses only two colors to delimit the areas covered by
James Cook and others. Later in that volume he published two maps of the route sailed by
the German expedition. Unfortunately, they discovered a finger of permanent pack ice stretching from the north to approximately 76°, which made progress further north impossible. Petermann was undaunted in his endeavors to reach the
North Pole and demonstrate a possible passage to the
Pacific Ocean, even after this expedition had failed in that respect. In 1869 he published a map of the
Arctic Ocean north of
Wrangel Island 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. As to the
Northeast Passage, Nordenskiöld's trip to the
Yenisei river in 1875 hinted at this being the easier route. The successful completion of the passage during Nordenskiöld's
expedition with the steamship
Vega was published in 1879 in PGM shortly after Petermann's death. The map was drafted on top of Petermann's 1873 map of Siberia. The route of the
Vega had also appeared on a Russian copy of Petermann's 1873 map. The PGM editors also added it in their 1879 map. This might have been a way to honour Petermann. The map shows clearly to what degree the descriptive data of older explorations (i.e.
Vasili Pronchishchev, 1735–36; Hariton Laptev, 1739–43;
Semyon Čeluskin, 1735–43;
Fyodor Minin and Dmitriy Sterlegov, 1740; and
Alexander Theodor von Middendorff, 1843) could be trusted when drafting a map from many sources and trying to amalgamate them into a single image. The difference between the coastlines on the two maps sometimes can be as much as ½° latitude and 1° longitude. Looking at the
Taimyr peninsula, the channel between it and the mainland is reduced from approximately 10 km to a few kilometres by the Swedish exploration. The only exception was the information derived from P.F. Anjou (1823), which was based on astronomical observations, and is the same in both maps. The article (translations from Swedish and Danish with a preamble by Behm) and map appeared four months after the
Vega had arrived in
Irkutsk. Hassenstein drafted the new map, maybe using the older draft. The title was hammered out of the old copperplate and replaced by a new one, while Nordenskiöld's data were engraved, and printed in red, making it look like an overlay on the old map. Because of the use of lighter background colors the newer map looks much fresher than the older one, though only six years lay between the two.
Australia Petermann kept his promise, made in the preface of the first issue of PGM, when he was responsible for the new edition of Stieler's Hand-Atlas. He also had a weakness for Australia. Up to his death he published some 48 maps concerning exploration in (parts of) Australia, though hardly any of the expeditions bore any German influence. In 1866, when he gave an account of the first issue of the fifth edition (1866–67) of the Stieler, he frequently referred to maps or articles published in PGM. Furthermore, he mentions that he is working on four other maps of Australia or parts of it. One of these is his famous eight-sheet map of Australia, scale 1:3,500,000, and the other three are concerned with exploration or based on land-property maps. (
Spezialkarte von Neu-Süd-Wales nach den Kataster-Aufnahmen, later published as
Spezialkarte eines Theiles von New South Wales (PGM, 12, 1866, table 13);
Spezialkarte vom See’ngebiet im Inneren von Australien, later published as
Das See’n-Gebiet (Lake District) und die Steinige Wüste (Great Stony Desert) im Innern von Australien (PGM, 13, 1867, table 4);
Karte der Entdeckungen im Inneren Australiens, scale 1:2,500,000, which he probably chose not to publish in PGM due to all the new discoveries). In 1871/72 he published the eight-sheet map as Specialkarte von Australien in 8 Blättern in Ergänzungsheft 29 (volume VI) and 30 (volume VII). It is a superb effort to compile all available knowledge in a colored map-image that measures 194x118 cm altogether, and it reminds us of the ten-sheet map of Africa of 1863. Being Petermann he would have liked to have accompanied it with a volume containing its ten-year history of exploration and discoveries, but in order not to raise the retail price of the map he satisfied himself with merely citing the volumes of PGM where the information could be found and providing an accompanying 43-page geographical-statistical compendium by C.E. Meinicke. In 1875 a second revised edition appeared, with a small sample in PGM. We unfortunately do not find his famous six-sheet map of the United States (
Neue Karte der Vereinigten Staaten vor Nord-Amerika in 6 Blättern) in the issues of PGM. It was produced for the sixth edition of the Stieler on scale 1:3,700.000, though a small part appeared in the next annual as an illustration of the exploration of Northwest Texas.
Source interpretations Several times Petermann indicated that he disagreed with the reports of explorers, probably basing his arguments on reports and literature at his disposal or on sound geographic reasoning. In a map, concerning among other things lake
Uniamesi, he tends to disagree with
Jakob Erhardt, one of the missionaries of the
Church Mission Society of London, concerning its situation and extension. Erhardt was erroneous in that he situated the lower tip of the lake around 13° South 36° East and made it bend westward to 28° East, with a probable extension to 24° East. Furthermore, he thought that
Lake Victoria,
Lake Tanganyika and
Lake Nyassa were one inland sea extending to 6° North. A lack of data led Petermann to agree with his erroneous shape of the lake or lakes, but he was not convinced of its wide extension to the west and north. As for the sources of the
Nile he was not so much mistaken, as they were indicated by a text near the equator between 30° and 36° East, but this was not so hard to induce. When one views the ethnographic and trade information in the map and interprets them from a relative topological point of view we can see this as the strength of the missionaries' reports. As their mission was focused on people and not on the natural environment this kind of information was of great importance to them. But geometrically their information could not be trusted, in part because most of their information was based on verbal reports of the native tribes. At other times he depicted maps of the same area from several authors together in one supplement map to show the authors' different interpretations. This was the case with, for example, the map of the
Kerguelen and
McDonald Islands sighted by John Heard (1853), William MacDonald (1854), Hutton (1854), Attway (1854), Rees (1854), and Neumayer (1857), with several comparisons of explorations since
James Cook. The same with small maps (scale ca. 1:33,000,000) of the central part of southern Africa, which shows different interpretations by
Heinrich Kiepert (1855), J. McQueen (1857) and
David Livingstone (1857). Or with the representation of the Gabon countries, which show interpretations by August Petermann,
Thomas E. Bowdich, William D. Cooley,
Heinrich Kiepert,
Paul Belloni du Chaillu and
Heinrich Barth. Many times he included an outline map of Germany, or parts thereof or other countries to show the vastness through which the explorers had to travel. This must have contributed to the understanding and compassion the readers felt for the sacrifice and hardships the explorers had to go through to come to the results presented in the articles and maps. ==Stieler-Handatlas==