On relationship between academicians: two unknown letters of S. O. Yefremov to V. I. Vernadskyi

The aim of the work. Publication of an epistolary heritage and research of contacts, relations and cooperation between literary critic, publicist and public figure, academician of the All-Ukrainian Academy of Sciences Serhii Yefremov (1876–1939) and first president of the Ukrainian Academy Volodymyr Vernadskyi (1863–1945). The research methodology is based on the application of historical and comparative methods, source and historiographical analysis and bibliographic heuristics. Scientific novelty of the work: for the first time two unknown (attributed by the author) letters of S. Yefremov to V. Vernadskyi, dated October 18, 1921 and April 19, 1922, were published and commented on. Based on the available sources, an attempt was made to reconstruct and analyze the relations and cooperation of the academicians, which are currently lacking from the historiography. In the first place, the correspondence, diary entries and mentions of both academicians were analyzed. Indirect sources (letters and memoirs of their colleagues, minutes of meetings of scientific and cultural institutions, etc.) were also used. The facts of their relationship (which was longest and most active in the Temporary Committee for the Establishment of the All-People's (National) Library of Ukraine) are tracked, stages of cooperation, displays of mutual support in difficult "conditions of the revolution", when even the academician's status didn't protect them from harassment and repressions, are considered. Emphasis is placed on the mutual respect between the scientists with possible factors behind their friendly relationship being indicated. An attempt at correspondence in 1921, when V. Vernadskyi returned from Crimea to Petrohrad, is analyzed. Conclusions. It is noted that both prominent personalities who engaged in active communication in matters concerning the development of Ukrainian science and culture in 1918–1919, failed to establish a further stable epistolary relationship. Still, V. Vernadskyi was fairly aware of the fate of the repressed S. Yefremov.