A final consonant is not doubled when it is preceded by a diphthong,
when the primary accent is either not on, or not retained upon, the
last syllable, or when the additional syllable begins with a consonant;
as, beat, _beating_, _beaten_; dif´fer, _dif´fering_, _dif´fered_,
_dif´ference_, _dif´ferent_; prefer´, _pref´erence_; refer´,
_ref´erence_; fit, _fitful_, _fitly_, _fitness_; ben´efit, _ben´efited_,
_ben´efiting_.
EXCEPTION I.—Compounds that remove the primary accent from
the point of duplication retain the double letter; as,
_broad´-brimmed_, _heel´-tapping_.
_Remark I._—When _ly_ is affixed to words ending in _l_, the
l is not considered doubled; as in _cool-ly_, _real-ly_,
_gravel-ly_, _royal-ly_.
_Remark II._—_Nutmegged_, _kidnapping_, _kidnapped_,
_kidnapper_, _zigzagging_, _zigzagged_, _excellence_, and
some others, are undisputed exceptions to the rule. There are
nearly one hundred words, from which more than four hundred
derivatives are formed, that are usually made exceptions to
this rule. Webster is distinguished for making nearly all the
derivatives conform to the rule. Webster and Smart accent the
verb _curv´et_, on the first syllable, with which accentuation
_curveting_ and _curveted_ are correct spellings; other
orthoepists accent upon the last syllable, then _curvet´ting_
and _curvet´ted_ are correct.