The language of Czech classical prose writers has been well characterised so far. Many Czech linguists have lately focused on the language of epistolography. Mainly, private letters drew their attention and this was due to (among other things) their immediality and close relation to the spoken language. Our project analyses the letters written by and addressed to Karel Havlíček, a Czech journalist and prose writer of the mid-19th century. A preliminary corpus consists of 548 transliterated letters (approximately 250.000 text words), which is a half of a total of more than 1.100 letters (of which there are about 350 in German and several others in further languages). The letters in foreign languages have to be translated for the edition in preparation. Search for an appropriate equivalent and its selection from a set of competing means inspire the linguist to carry out a research into the mid-19th c. Czech. This paper describes the usage of words selected out of the corpus, e.g. some kinds of conjunctions and particles, and reflects on the criteria for selection of appropriate equivalents for translation. Its wider task is a description of the mid-19th c. Czech based on reliable data and indication of some possibilities for further research.