Johann Gottlob Lehmann
Johann Gottlob Lehmann
Johann Gottlob Lehmann established the foundations of stratigraphy, or the scientific study of sedimentary rocks with regard to their order and sequence. His Versuche einer Geschichte von Flotz-Gebrugen (1756), in which he classified mountains and established a theory of their origins, was the world's first geologic profile.
Lehmann was born on August 4, 1719, in Langenhennersdorf, then in the state of Saxony but now a part of Germany. He earned his M.D. at the University of Wittenberg in 1741, and went on to a medical practice in the city of Dresden. While working as a doctor, however, he discovered something that interested him more than medicine: rocks.
His amateur fascination with mines and mining soon turned into a vocation, and by 1750 the 31-year-old Lehmann had published a number of papers on ore deposits and their chemical makeup. These publications helped lead to an official commission from the Royal Prussian Academy of Sciences in Berlin to study mining as practiced in various parts of Prussia.
Six years later, in 1756, Lehmann published his classic, Versuche einer Geschichte von Flotz-Gebrugen. In it he observed that the placement of rocks on the Earth's surface or below it is not random; rather, it reflects a history (Geschichte) in geological terms. Obvious as this idea might seem now, it was far from apparent in Lehmann's time, and not only did his book establish a framework for stratigraphy, it also spurred on local geology, or the investigation of specific sites.
In 1761 Lehmann joined the ranks of the many German scientific minds recruited for the Imperial Academy of Sciences in St. Petersburg, Russia. He became professor of chemistry, as well as director of the natural history collection at the Academy, but he remained interested in affairs back in Germany. Thanks to his efforts, a research institute called the Freiberg Bergakademie was established in his homeland in 1765.
While in Russia, Lehmann conducted a number of field investigations. For instance, in 1761 he traveled to the Beresof Mines on the eastern slopes of the Ural Mountains, and there gathered samples of an orange-red mineral. He called it Siberian red lead, and after studying it in St. Petersburg, described it as containing lead "mineralized with a selenitic spar and iron particles." This was in fact an early description of what would be identified in 1797 as chromium, a new element.
By that time, however, Lehmann was long dead, having passed away in St. Petersburg on January 22, 1767, at a mere 47 years old. His field studies in Russia later became an example for investigations of geologists who followed him.