hart's work has been lauded by modern linguists for his highly insightful phonetic analysis of the early modern english of his days, and for his thoroughness in pursuing the phonetic principle. his discussion of vowel pronunciations is particularly interesting to historians of the english language, because it documents the spoken english at an intermediate point during the great vowel shift, which during hart's days was radically transforming the vowel system of english. thus, for instance, hart documents that the pronunciation of words that had middle english long but shifted to in modern english was still variable in his days, with some speakers retaining in some words, but a diphthong (spelled "ei" by hart) already common in others.