This paper takes issue with Biber's (1988) findings concerning the significance of infinitives for what he calls the "overt expression of persuasion" (Biber 1988: 115). It aims to demonstrate that statistically generated results of research on large electronic corpora of contemporary English may not be verifiable in small, well-contextualised, single-genre collections, such as the one representing 19th century English used in this study. The collection comprises denunciation letters addressed to the colonial authorities (the Colonial Office) by the first British settlers in the Cape Colony (the 1820 Settlers). The letters follow the generic model of petition (Włodarczyk 2010) understood as an official written request. An act of denunciation, as we may assume, contributes to the inherent persuasiveness of petitions by increasing the illocutionary force (in the sense of Searle 1969, 1979) of the letter. Therefore, patterns of distribution of infinitives as markers of persuasion (Biber 1988) are particularly interesting to trace in the 1820 Settler denunciation letters. The paper shows that some of Biber's statements may not be taken as valid generalizations, as the persuasive potential of infinitives may not be corroborated unless each and every token is thoroughly contextualized. Furthermore, an analysis of requests in denunciations conducted within Speech Act Theory (Austin 1962; Searle 1969; Blum-Kulka 1984; Culpeper and Archer 2008) shows that it is first and foremost politeness concerns (cf. Brown and Levinson 1987), not the increased need for persuasiveness, that determine the degree of the illocutionary force of requests.
In 1820, the Cape of Good Hope, a British colony since 1795, became the new home to c. 4,500 English-speaking settlers. Correspondence surviving from this period in reference to this settlement enables insights into early nineteenth century letters, a still understudied area. Moreover, it provides a good setting to disambiguate the term letter from an internal, bottom-up perspective. Such a perspective may offer "a key for disclosing historical forms of communication" (Hübler and Busse 2012: 1) as first-order phenomena. This is achieved in an analysis of categorial labels (keywords) and metacommunicative clues found in the internal correspondence of the Colonial Office, a British government department, in the years 1820-1821. The results of the analysis provide a partial answer to what the label letter meant for this professional community. Adding a researcher’s perspective to such a description allows proposing a twofold approach to "the letter" as an analytic category in the study of historical correspondence.