The most proscriptive eighteenth-century grammar of English, according to Sundby et al. (1991), is Knowles's Principles of English Grammar (1796). With 722 comments in which grammatical mistakes are criticised, Knowles heads the list which Sundby et al. compiled for their Dictionary of Normative Grammar. The copy of Knowles's grammar which Sundby et al. analysed was the fourth edition; the grammar had first come out in 1785 in Liverpool, and it enjoyed a moderate popularity (Alston, 1965:78–9). The fourth edition of Knowles's grammar consists of 144 pages, which makes it considerably longer than the first edition (36 pp.) (Alston, 1965:79). Fifteen pages of the book are devoted to a section called ‘Of Verbal Criticism’. This section includes according to Sundby et al. (1991:8) ‘some 460 “improper” sentences [which] are presented in alphabetical order …, the “proper” form of (the relevant part of) each sentence being given on the right’. In addition, the book contains an appendix with ‘Exercises of False Construction’, which are included to ‘afford the schoolboys and teachers for whom the grammar was intended ample opportunity for testing their linguistic ability, improved (it may be supposed) by diligent study of the first two lists’.