EN
The article contributes to the studies of Polish language in Lithuania (Kowno region). The authoress analyses letters of the 19th century historian and lexicographer, Szymon Dowkont written to the other contemporary historian Teodor Narbutt. She considers phonetic, inflectional and syntactic examples. As a result she has distinguished in the studied language: 1) regional features typical for the dialect of north-east borderland and 2) the features connected with Polish-Lithuanian bilingualism of the author of the letters.