The Cambridge History of English and American Literature in 18 Volumes (1907–21).
VOLUME XVIII. Later National Literature, Part III.
§ 6. Conservatisms and Radicalisms; American Pronunciation
American English is in some respects archaic. It has never developed, for example, the swooping diphthongs that, since the end of the eighteenth century at least, have characterized the British pronunciation of 
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,