John Lewis authored the language textbook "A Graduated English-Welsh Spelling Book" in the 19th century. The purpose of the book is to assist Welsh speakers in learning English spelling and enhancing their written English abilities. The book is laid out in a series of graduated courses that start with simple English vocabulary and work their way up to more difficult terms and expressions. Each lesson provides a list of vocabulary along with their Welsh equivalents, exercises to help with spelling and pronunciation, and a pronunciation guide. English grammatical rules are explained and given instances in both Welsh and English in the book's section on the subject. Verb tenses, sentence construction, and other language-related issues are all covered in this section. Welsh speakers who want to get better at English and English speakers who want to study Welsh can both benefit from this useful tool.