Page 133 - Webster's Speller

3. Verbs having a digraph, diphthong, or long vowel sound before the last consonant, do not double that consonant.
seal, sealed, seal-ing, seal-er; heal, heal-ed, heal-ing; oil, oiled, oiling; hail, hailed, hail-ing; claim, claimed, claim-ing, claim-er; cool, cooled, cool-ing, cool-er; ap- pear, ap-peared, ap-pear-ing, ap-pear-er; re-peat, re- peat-ed, re-peat-ing, re-peat-er, re-coil, re-coiled, re- coil-ing, ve-neer, ve-neered, ve-neer-ing, ve-neer; a- vail, av-ailed, a-vail-ing, re-strain, re-strained, re- strain-ing, re-strain-er.
4. Verbs ending in two consonants do not double the last.
gild, gilded, gild-ing, gild-er; long, longed, long-ing, long-er; watch, watched, watch-ing, watch-er; dress, dressed, dress-ing, dress-er; paint, paint-ed, paint-ing, paint-er; charm, charmed, charm-ing, charm-er; re- sist, re-sist-ed, re-sist-ing, re-sist-er; con-vert, con-vert- ed, con-vert-ing; dis-turb, dis-turbed, dis-turb-ing, dis-turb-er.
5. Verbs ending in a single consonant, preceded by a single vowel, the last consonant or syllable not being accented, ought not to double the last consonant in the derivatives.
bi-as, bi-ased, bi-as-ing; bev-el, bev-eled, bev-el-ing; can-cel, can-celed, can-cel-ing; ca-rol, ca-roled, ca-rol- ing; cav-il, cav-il-ed; cav-il-ing; chan-nel, chan-neled, chan-nel-ing; chis-el, chis-eled, chis-el-ing; lev-el, lev- eled, lev-el-ing; coun-sel, coun-seled, coun-sel-ing; cud-gel, cud-geled, cud-gel-ing; driv-el, driv-eled, dir- vel-ing; du-el, du-eled, du-el-ing; e-qual, e-qualed, e- qual-ing; gam-bol, gam-boled, gam-bol-ing; grav-el,
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