reasonable number of measuring points for precipitation and temperature maps would be 1,500 and 600 per 100,000 km² respectively to create acceptable isoline maps for these phenomena). These give schematic negative relief maps, which hardly even approximate the true relief of the territory. Thoulet wanted to show that the few bathymetric measurements available for the vast oceans would only vaguely approximate the true relief of the ocean floors. Petermann must have had the same idea intuitively for his exploratory maps. He was keen, however, to introduce spot heights and spot depths in the maps he drafted in order that others could benefit from them. Technical innovations Having understood well from his teacher, Heinrich Berghaus, the merit of the metric scale he introduced the representative fraction as map scale, without discarding, however, the verbal better known or local scale. The popular acceptance of the metric system and Greenwich as prime meridian was slower in the uptake. Only with the ninth edition of Stieler's Hand-Atlas (1900–1905) was this process completed. In 1870 Petermann advocated the use of a red and blue color scheme for temperature maps of the oceans. Although the number of projection methods increased at a reasonable rate, a few well-known sorts, like the stereographic and orthographic equatorial projections and the projections of Lambert, Flamsteed and Mercator, remained the most popular. Petermann did publish reports on the new projection methods of J. Babinet (1854) and J. James (1857), and G. Jäger, but he hardly used them. Though Petermann and Ernst Behm (1830–1884; like many of the famous Gothaer geographers and cartographers Behm had first another profession. He was a physician, who learned the geographic trade in practice) wrote many articles about geodesy and surveying, they rarely got involved in other technical and theoretical cartographic issues. Petermann concerned himself much more with printing technology, especially colour-lithography. Although they produced many color maps in this way in the 1870s, more and more maps returned to hand coloring, for it then became cheaper than lithography. According to Stams, the Gotha Institute may have produced some 2,500,000 hand-colored maps for all its cartographic products in a decade, or 800 per day! In his last article published before his death, Petermann speaks enthusiastically about the newly developed photogravure, which considerably reduced costs per map while also increasing production speed. In his opinion the 715-sheet Austrian map was probably twenty times more efficiently produced than an