In the 18th and 19th century several German and Baltic-German scientists investigated almost unknown territories of the Russian Empire. Many of them were invited by the Russian Imperators and some became academicians of the St. Petersburg Academy of Sciences,and later had considerable influence on the development of science in Russia in general and on the organization of expeditions to the Far East and Siberia in particular. German naturalists like Georg Wilhelm Steller (1709-1746), Johann Georg Gmelin (1709-1755), Peter Simon Pallas (1741-1811), Karl Ernst von Baer (1792-1876), Ferdinand von Wrangell (1797-1870) and Alexander Theodor von Middendorff (1815-1894) traveled through Siberia collecting information about flora, fauna, geology, climate, ethnology,history and economy of the Far East of Russia. Their results were published in Russian, German and French,mostly in journals of the Russian Geographical Society (St. Petersburg), in travelogues or in separate monographs and book-chapters. Results of investigations of the Russian Empire became available in Europe by special scientific journals edited e.g. by P.S. Pallas, J.G. Georgi, Th. Fr. Ehrmann, A. Erman, K.E. v. Baer and G. v. Helmersen. The western world was first informed about frozen ground in Siberia by J. G. Gmelin, who reported finding the phenomenon in Yakutsk, but Leopold von Buch (1774-1853) doubted his report and argued that plants were growing in this region, which considered impossible on permanently frozen ground. As a result, he demanded that Gmelin’s data be removed from scientific textbooks [1]. On behalf of a merchant of the Russian-American Company, Fedor Shergin, a shaft was dug in Yakutsk to get drinking water. To Shergi’s surprise he was unable to reach liquid water, but the governor of the Russian- American Company, Ferdinand von Wrangell, requested him to continue digging at the expense of the Company, for studies of the frozen ground underneath Yakutsk. The sinking of the well, starting in 1828, has been continued until 1837 reaching an end depth of 382 English feet (about 116.5 m), without reaching unfrozen soil [2]. The shaft developed great importance for further geocryological studies. First measurements of soil temperature were carried out therein in April 1829 by the German physicist Adolph Erman (1806-1877). Down to the bottom depth of 46 Paris feet (about 15 m) at that time he recorded continuously -6 °R (-7.5 °C) in all deeper parts of the well, which corresponded very well with the mean annual temperature of Yakutsk of – 5.9 °R. This result can be credited as a first finding of the permafrost depth of “Zero Annual Amplitude”. Assuming a geothermal gradient of 1 °R/100 feet, Erman expected liquid water in a depth of 600 feet (about 190 m) [3] but Shergin’s measurements published in 1838 indicated temperatures of -0.5 °R at the end bottom of the shaft (116.5 m) [2]. Several scientists were doubtful about Shergin’s data [3]. Between 1838 and 1843 Karl Ernst von Baer compiled all data available on frozen ground in Siberia, from sources either published or from Russian archives. He wrote a special permafrost study including the first classification of permafrost and made suggestions for regular observations in Shergin’s shaft. Baer and the commission responsible formulated instructions for an expedition to eastern Siberia initiated by Baer and led by Alexander Theodor von Middendorff with the focus to investigate the region north of Turukhansk to the Chatanga River and to investigate permafrost, especially its thickness, temperature and distribution [4]. Baer also drew the first map of permafrost distribution. Unfortunately his permafrost study and this permafrost map were not published before 2000 [5]. Baer also suggested that investigations of air and soil temperatures be carried out in British North America [6]. According to Baer’s guide in 1843-1845, Middendorff carried out soil temperature measurements at Turukhansk and other Siberian places. In the Shergin shaft in Yakutsk, regular measurements, started by him in 1844, had been continued until 1846 by local observers. Middendorff reported a bottom temperature in the shaft of -2.4 °R. He published his geothermal investigations in great detail, including data on the thermal conductivity of soils, which were a result of the geothermic measurements in Shergin’s shaft [7].As Erman had also earlier assumed, he supposed a permafrost depth of 600 feet beneath Yakutsk. Baer began a long discussion with him about his conclusions and the geothermal gradient he reported [8](cf. also [9]). Middendorff’s collection of permafrost observations in Siberia and his conclusions for the geographical distribution and thickness of permafrost provided the foundation for a generation of geocryologists. Temperature measurements in the active layer were carried out within the framework of the International Polar Year 1882-1883 at Sagastyr Station in the Lena River delta and on Novaya Zemlya. Soil temperature observations had been included in the meteorological program and were carried out regularly at 0.4 m, 0.8 m and 1.6 m depths [10]. The medical doctor Alexander von Bunge (1851-1930) was a participant of this expedition. He described the place on Bykovsky Peninsula where Adams found the first mammoth carcass in 1799 and reported on other mammoth carcasses found in the Lena Delta, and on permafrost soils, polygonal structures and ice wedges that he observed. He published a hypothesis on the genesis of ground ice by thermal contraction [11]. In 1885-1886 Bunge was the leader of the expedition of the St. Petersburg Academy of Sciences to the New Siberian Islands during which he and his companion Eduard von Toll (1858-1902) found mammoth relicts and studied the ground ice formations on Great Lyakhovsky Island. European scientists were deeply impressed by the first photographs of huge ground ice wedges published by Toll. He speculated that these formations were relicts of glaciers and introduced terms like “fossil ice“and “ice rock”(Steineis) into geocryology [12]. References: [1] Buch, L.v.: Einige Bemerkungen über Quellen-Temperatur. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin aus dem Jahre 1825, Berlin (1828): 93-105 [2] Helmersen, G.v.: Notiz über einen in der Stadt Jakutsk angelegten Brunnen. Bulletin scientifique publié par l’Academie Impériale des Sciences de St.- Pétersbourg 3, H.13 (1838): 193-198 [3] Erman, A.: Extract from a letter dated Berlin March 5, 1838. The Journal of the Royal Geographical Society of London 8 (1838): 212-213 [4] Baer, K.E.v., Brandt, F., Lenz, E., Meyer, C.: Instructions donnees a M. le docteur de Middendorff,pour son voyage en Siberie. Bulletin de la Classe physico-mathematique de l’Académie Impériale des Sciences de St.-Pétersbourg, T. 1 (1843): 177-185 [5] Bér, K. M.: Materialy k poznaniju netajuscego pocvennogo l’da v Sibiri. Pod. red. R. M. Kamenskogo. Jakutsk, Institut merzlotovedenija SO RAN (2000) (in Russian) [6] Baer, K.E.v.: Materialien zur Kenntniss des unvergänglichen Boden-Eises in Sibirien. Unpublished manuscript; commented by Erki Tammiksaar; edited by Lorenz King. Berichte und Arbeiten aus der Universitätsbibliothek und dem Universitätsarchiv Giessen, Bd. 51 (2001) [7] Middendorff, A.T.v.: Geothermische Beobachtungen. In: Reise in den äussersten Norden und Osten Sibiriens: Einleitung, Klimatologie, Geognosie. St. Petersburg, Bd. 1 (1) (1848): 83-183, Taf. XII-XIV [8] Baer, K.E.v.: Ueber nothwendig scheinende Ergänzungen der Beobachtungen über die Boden- Temperatur in Sibirien. Bulletin de la Classe physicomathematique de l’Académie Impériale des Sciences de Saint-Pétersbourg, T.VIII No. 14 (1850):209-224 [9] Shiklomanov, N.I.: From exploration to systematic investigation: development of geocryology in the 19th- and early-20th-century Russia. Physical Geography 26, 4 (2005): 249-263 [10] Wood, K.R., Streletsky, D.A.: Soil and permafrost temperature data obtained during the First International Polar Year 1882-1883. 9th International Conference on Permafrost, Fairbanks, USA, Vol. 2 (2008): 1957-1962 [11] Bunge, A.v.: Einige Worte zur Bodeneisfrage. Rus. K. Min. Gesell. Verh. 2. Ser., V.40 (1902):203- 209 [12] Toll, E.v.: Iskopaemye ledniki Novo-Sibirskikh ostrovov, ikh otnoshenie k trupam mamontov i k lednikovomu periodu (Ancient glaciers of New Siberian Islands, their relation to mammoth corpses and the Glacial period). Zapiski Imperatorskogo Russkogo Geograficheskogo obshestva po obshei geografii (Notes of the Russian Imperial Geographical Society) 32 (1897): 1–137 (in Russian) [13] Baer, K.E.v.: South boundary of permafrost in Siberia. St. Petersburg: Department of the Archives of the Academy of Sciences of Russia, f. 129, op.1, No. 759, I.1.