Józef Kowalewski, a founding father of Mongolian studies in Russia, stayed in Beijing from November 1830 until July 1831. He stayed with the Russian Ecclesiastical Mission and, being a Catholic himself, Kowalewski was very interested in the history and current state of Catholicism in China. In those years Catholicism in China faced severe persecution. All European missionaries were expelled from China with the exception of Bishop Gaetano Pirès Pereira, who was allowed to stay at the Russian Mission because of his old age. Kowalewski is said to have written a history of Catholicism in China which was destroyed by fire. However, unpublished diaries of Kowalewski, which survive in the Russian archives, contain much interesting information about Catholic cemeteries in Beijing, the life of Chinese converts, the Jesuit library and records of his talks with the last Catholic bishop.