(b. Gammelbo, Västmanland, Sweden, 11 March 1712; d. Stockholm, Sweden, 17 October 1772)
Tilas’ father, Olof Tilas, was an officer and landowner who was knighted in 1719. His mother, Maria Hjärne, was the daughter of the scientist Urban Hjärne. As was usual among the Swedish landed gentry at that time, Tilas received his elementary education at home and was sent to the University of Uppsala in 1723, studying there until 1726 and again from 1728 to 1732. According to his unpublished autobiography, he did not spend much time on studies and gave the university little credit for his education. This is certainly unfair, for he received a good foundation in both Latin and the natural sciences, the latter most probably from his connection with the group around Linnaeus.
Tilas’ interest in mining began early, and in 1732 he became assistant (auskultant) at the Office of Mines, the state organization that had administrative and legal control of the flourishing Swedish mining industry. He was greatly interested in the inspection of mines and took part in the work at mines and smelting plants. He discovered the need for exact mapping of the mineral veins in the mines, in order to form rational plans, and soon extended this work to mapping the geology of the surrounding areas, to facilitate prospecting for new mines.
Tilas developed an ambitious project to map all of Sweden geologically; and from his correspondence it seems that he also planned a geological map of the world. His inspiration certainly was Linnaeus’ plans for similar inventories of the fauna and flora of the world. Tilas produced an unpublished geological map of two provinces of Finland and of a large number of mines. His grand designs were not approved by some of his older colleagues, but his results and ideas made him famous. He was a founding member of the Royal Swedish Academy of Sciences (1739) and served as its president for two terms. From 1741 to 1743 and in 1745 Tilas was a member of the international commission to establish the border between Sweden and Norway. With some of the younger members he walked along the boundary, making a number of interesting geological and other observations in relatively unknown and inaccessible areas.
In 1751 a fire destroyed Tilas’ house; and his collections of rocks and minerals, and all his manuscripts and maps, were lost. Loss of the latter was especially disastrous to his great plans, and it was impossible for him to repeat all the fieldwork involved. Some of his results were published in 1765, but much of his scientific work remains in the manuscripts he managed to reconstruct and in the form of unpublished reports. Tilas’ great importance lay not only in his plan to make geological maps of large regions but in his activity in other fields of geology. Some of his views on the origin of fossils and erratic boulders seem rather modern; and he introduced a number of terms, including the mineral name feldspar. He was also one of the first geologists to work with oil (1740) and to describe its economic exploitation.
Tilas was married in 1741 to Hedvig Reuterholm (d. 1743) and in 1743 to Anna Catharina Åkerhielm. Through both his marriages he became connected with influential political families and was active at the royal court. Also interested in genealogy and numismatics, Tilas became chamberlain in 1766 and state herald in 1768.
I. Original Works. Tilas’ works include En bergmanns rön och forsök i mineralriket (Stockholm, 1738); “Mineralshistoria øfver Osmundsberget uti Rättviks Socken,” in kungl. Vetenskaps akademiens Handlingar (1740); Stenrikets historia (Stockholm, 1742); and Utkast til Sveriges mineralhistoria (Stockholm, 1765). Complete lists his published papers are given in the secondary literature. His unplished diaries and official reports, preserved in Swedish archives, have been used extensively in the study of the politics and culture of his time.
II. Secondary Literature. Much of the extensive but rather scattered literature on Tilas is based in his unpublished diaries, MSS. and reports. See E. V. Falk, “Daniel Tilas och Fredrik Gyllenborg,” in Personhistorisk tidskrift, 36 (1936), 19–49; G. Regnell, “On the Position of Palaeontology and Historical Geology in Sweden Before 1800,” in Arkiv för Mineralogi och Geologi, 1 , no. 1 (1949), 1–64; and N. Zenzen. “Gelogiska kartor och geologisk kartäggning i Sverige fØre upprättande av Sveriges Geologiska Undersökning,” in Geologiska föreningens i Stockholm fökning,” in Geologiska öremingnes i Stockholm förhandlingar, 47 (1925), 311-343: “On the First Use of the Term ’Feldspat’ (Feldspar etc.) by Daniel Tilas,” ibid., 385-405: and “Daniel Tilas om geologien i svensk-norska gränstrakter,” ibid., 53 (1931), 27-46.