The Notion of persistent rule in historical phonology has been discussed by Chafe in his important asticle on the order of phonological rules (Chafe 1968). Two examples are the wellknown devoicing of final obstruants in German - a rule added to the grammar of German at a point in time in its history, and still operative so that words introduced after the adding of the rule are subject to it; and the loss of final /n/ in Livonian, so that a word like /nainen/ first becomes /naine/, then is subject to a rule that eliminates final vowels, thus becoming /nain/, which, since the n-dropping rule is still in force, becomes /nai/. Rules are said to persist when they apply either to forms resulting from rules added later than they to the grammar of the language, or to forms introduced into the language from a source other than a later rule, i.e. through borrowing.