ABSTRACT The paper discusses the geographical distribution of the monophthongisation of (1) the diphthong [ei] ( [e:c]) before the palatal fricative [c] (i.e. [eic i:c]) and (2) the diphthong [ou] ( [o:x]) before the velar fricative [x] (i.e. [oux u:x] in words like high an bough. The resulting monophthongs became the input to the diphthongisation rule, a part of the Great Vowel Shift. On the basis of forty-nine Middle English poetic texts from the Chadwyck-Healey online corpus un effort is made here to establish temporal and dialectal conditioning of the change.
