Monosyllables and words having the primary accent on the last syllable,
when they end with a single consonant preceded by a single vowel,
double their final consonant before an additional syllable that begins
with a vowel; as, wet, _wetter_, _wettest_, _wetting_, _wetted_; drum,
_drumming_, _drummed_; dispel, _dispelling_, _dispelled_.
EXCEPTION.—A final _x_, or the _s_ in gas, should not
be doubled; as, fix, _fixes_, _fixed_, _fixing_; annex,
_annexing_; _gases_, _gasefy_.
_Remark I._—_U_ after _q_ is never reckoned a part of a
diphthong or triphthong; so that from quit are formed
_quitting_, _quitted_; and from quag, _quaggy_.
_Remark II._—This rule applies only to derivatives which
retain the accent of their primitives, and not to such as
_in´ferable_, _in´ference_, _pref´erable_, _pref´erence_,
_ref´erable_, and _ref´erence_, from infer, prefer, and refer.
To the forms _infer´rible_, _refer´rible_, which are sometimes
met with, the general rule applies. _Transfer´able_, from
transfer, is an exception to the general rule; the regular form
_transfer´rible_ is not often used. Although _parallel´ogram_,
from par´allel, and _modal´ity_ from mo´dal, remove the primary
accent to the point of duplication, they do not double the
final _l_. See Remark II. under Rule VII.