This book presents an investigation of a number of areas of interest in the study of language change, dealing in particular with questions of how patterns of pronunciation vary across both time and space. Most of the illustrative material is drawn from non-standard dialects of English, especially the varieties spoken in Ireland (Hiberno-English). The theoretical issues discussed include the following: what role do articulatory and linguistic constraints play in determining the direction of sound change? How do social and political pressures influence the resolution of competition between conflicting local non-standard linguistic norms? Besides addressing such general issues, the book also offers insights into several specific areas in the history of English, both in its standard and vernacular forms. It will thus be of interest to English-language specialists as well as to historical linguists, sociolinguists and phonologists.