The authors express grateful acknowledgement to the librarians of City University Library (London) who helped the second author to consult The Athenaeum marked copies collection. The authors acknowledge also the two anonymous referees for their remarks and suggestions.
It is well known that Hugh MacColl (1837-1909) interrupted his logical investigations around 1884 for about thirteen years, a period which he mainly devoted to literature. In a letter to Bertrand Russell (1872-1970), dated 17 May 1905, MacColl recalls this break and tells how it was the reading of Lewis Carroll’s Symbolic Logic in 1896 that led him to reinstate his logical studies:‘
When, more than twenty-eight years ago, I discovered my Calculus of Limits [...], I regarded it at first as a purely mathematical system restricted to purely mathematical questions. [...] When I found that my method could be applied to purely logical questions unconnected with the integral calculus or with probability, I sent ...