It has been established by Henry Lee Smith Jr. and Edgar H. Sturtevant that the Germanic Verschärfung is due to the original presence of laryngeals. Both, however, seem to have been puzzled by the appearance of this phenomenon after u, in cases like Swed. rugg ‘shaggy hair’ and Norw. dial. rugga ‘carpet of shaggy hair’ beside ON rǫgg, rǫggr ‘long coarse wool’. According to Sturtevant, ‘we may assume that in Swed. rugg the Verschärfung has spread from the form with IH rъHW- > IE rəhw- to a related form with rhu- > IE ru-.' He holds that ‘a similar explanation is available for the vocalism of Goth, skuggwa “mirror”, bluggwans “struck”, OIcel. tryggr “true”, etc.’ but seems reluctant to admit that IH ihy and uhw should have yielded IE ihy and uhw (whence the Germanic Verschärfung), since nothing appears to warrant the hypothesis that ‘an IH voiceless laryngeal when preceded and followed by the same semivowel behaved in the same way as a voiceless laryngeal after ъ and before a semivowel.’ Sturtevant's explanation, however, offers no solution for the baffling alternate development of IH uhw- in Indo-European pointed out by Smith and attested by ON rȳja ‘to pluck wool', with a long vowel, like ON brū ‘bridge’, trū, trūa ‘faith’, būa ‘to dwell’, alongside of ON bryggja ‘pier, bridge’, tryggja, tryggva ‘to make firm’, byggja ‘to inhabit’. Though stating that this phenomenon, found throughout Indo-European, is particularly evident in Germanic and should explain ū in the 2d class of strong verbs (type of OE sūpan), Smith does not inquire any further into its origin. He merely enumerates a few possibilities, among which two deserve special notice: the alternate development might be due either to ‘an accent shift in certain classes of words which returned the accent to the root vowel after the reduction of the diphthong in time for the laryngeal to lengthen the u in pre-IE times’ or to a particular ‘syllabification of roots containing laryngeals’.