Unknown works of the orientalist B. A. Dorn devoted to the Arabian astrolabes

The article reveals new aspects of the scientific activity of the Russian orientalist Academician B. A. Dorn, who lived in the middle of the 19 th century (1805-1881). Over almost forty years B. A. Dorn was the head of the Asian Museum in St. Petersburg (now the Institute of Oriental Manuscripts, Russian Academy of Sciences). The main Dorn's scientific contribution is considered to be the vast catalogue of Oriental manuscripts and also the study of ethnography, philology, and history of Caspian Sea peoples and the Afghans. Little is known about that that B. A. Dorn was interested all his life in scientific instruments of the past: quadrants, celestial globes, planispheric astrolabes - first of all, of the Arabian origin. In his works, he described both foreign and Russian instruments possessed by state institutions and private owners. Some works written by B. A. Dorn in 1838-1865 are, in fact, the continuation of a unified study of Arabian planispheric astrolabes. These works have so far remained unknown to Russian science historians due to several reasons. The specialists, who studied the main activity of B. A. Dorn, disregarded these works because the latter are found outside the domain of philology. After B. A. Dorn's death the studies of the instruments were not continued by anyone and there were still no references to them in Russian works. At the same time, B. A. Dorn's works have become known to foreign researchers because they were written in German, and some of them were reprinted in Germany in 1990, later digitized in the Google Books project. Expert Western researchers, e.g. David King from Frankfurt am Main Institute for the History of Science, refer to B. A. Dorn's works. The study of the works of the Russian orientalist elucidates the fate of some astronomic instruments of the Arabian origin and supplements their modern description. The question is posed about the priority of the Russian scientist in the composition of the first description of Arabian astronomic instruments (in 1865), among which there were 24 planispheric astrolabes, including six Russian ones. The major scientific activity of B. A. Dorn as the orientalist is more deeply analyzed within his work at the Imperial Academy of Sciences and his interaction with other researchers, state and religious figures of the middle of the 19 th century. Moreover, the article demonstrates the importance of the investigation of scientific instruments of the past because they represent the technological, scientific, cultural, and artistic imprint of past epochs and are a kind of depositories of the knowledge gained.