§ 17] The Vowels 21 in M HG.; whereas eu became iu in OHG. when originally followed by an i, j or u in the next syllable, and this iu became ü (written iu) in MHG., even after the !, j or u had been weakened to e. This law explains the difference between the diphthong ie in the infinitive and the simple vowel iu (= u) in the three persons singular of the present indicative of verbs belonging to the second ablaut-series (§§ 12, 78), as OHG. biogan, to bend, pres. sing, biugu, biugis(t), biugit; MHG. biegen, „ „ „ biuge, biuges(t), biuget. Cp. further tief (OHG. tiof), deep, beside OHG. tiufi, depth; lieht (OHG. lioht), a light, beside liuhten (OHG. liuhten from *liuhtjan), to light. NOTE.—The iu in the above and similar examples must not be confounded with the iu in the OHG. and MHG. combination iuw which arose from prim. Germanic eww (= euw), and ewj, as triuwe (OHG. triuwi, Goth, triggws), true; triuwen, trūwen, to trust, pret. triuete, triute, trūte ; riuwe (OHG. riuwa), regret, bliuwen (OHG. bliuwan, Goth, bliggwan), to strike, and simi- larly, briuwen, to brew, kiuwen, to chew, riuwen, to regret; niuwe (OHG. niuwi, Goth, niujis, prim. Germanic stem-form *newja-), new. This iu before w never interchanged with MHG' ie from prim. Germanic eu, and explains why the strong verbs bliuwen, &c. have iu in all forms of the present. § 17. Accented primitive Germanic ai ( = Goth, äi) became ē in OHG. before r, w, Germanic h (cp. § 23, i), and finally; in MHG. it appears also as ē before the same consonants and finally, as mere, mēr (OHG. mēro, Goth, maiza), more, leren (OHG. leren, Goth, lāisjan), to teach; sēle (OHG. sela, older sëula, Goth, säiwala), soul; snē (OHG. snēo, Goth, snäiws), snow, gen. OHG. and MHG. snēwes; spiwen, to spit, pret. spē (OHG. spēo, Goth, späiw); dīhen, to thrive, pret. dich (OHG. dēh, Goth, däih); wē (OHG. we, Goth, wai), woe I; in all other cases ai became ei in both OHG. and MHG., as stein