English this sound is expressed by ey in prey, by ay in pray, by a in gate, and by ai in sailor. The gutturo-labial sound of the Italian o should be written au, which the French pronounce o. For etymological purposes also this plan would be preferable, as it frequently happens that an o (au), if followed by a vowel, has to be pronounced av. Thus in Sanskrit bhu, to be, becomes bhau (pronounced bho), and if followed by ami, it becomes bhav-ami, I am.
The diphthongs, where the full or long guttural a is followed by i and u, should be written ai and au. "To buy" would have to be written bai; to bow, bau. Whether au coalesce entirely, as in German, or less so, as in Italian, is a point which in each language must be learned by the ear, not by the eye.
Most people would not be able to distinguish between ai and ei. Still there is a difference; as, for instance, in German kaiser and eis. Even in English the sound of ie in "he lies" is said to be different from that of "he lies." Where it is necessary to mark this distinction, our diagram readily supplies ai and ei.
The diphthong eu is generally pronounced so that the two vowels are heard in succession, as in Italian Europa. Pronounced more quickly, as, for instance, in German, it approaches to the English sound of oy in boy. According to our diagram, we should have to write ĕi and ĕu; but ei and eu will be preferable for practical purposes.
The same applies to the diphthong ŏi. Here, also, both vowels can still be heard more or less distinctly. This more or less cannot be expressed in writing, but must be learned by practice.
The last diphthong, on the contrary, is always pronounced like one sound, and the deep guttural o seems to be followed, not by the vowel u, but only by an attempt to pronounce this vowel, which attempt ends, as it were, with the semi-vowel w, instead of the vowel. In English we have this sound in bought, aught, saw; and also in fall and all.
The proper representation of these diphthongs would be ŏi and ŏu; but oi and ou will be found to answer the purpose as well, except in philological works.
For representing the broken sounds of a, o, u, which we have in German väter, höhe, güte, in the French prêtre, peu, and une, but which the English avoids as sounds requiring too great an effort, no
