-- where they are pronounced today is indicated by the arrows.
The nucleus of the two high vowels (front "long i" /i:/, and the back
"long u" /u:/) started to drop, and the high position was retained only
in the offglide. Eventually, the original /i:/ became /ai/ - so a "long
i" vowel in Modern English is now pronounced /ai/ as in a word like 'bite':
/bait/. Similarly, the "long u" found its nucleus dropping all the way
to /au/: the earlier 'house' /hu:s/ became /haus/. All the other long
vowels rotated, the mid vowels /e:/ and /o:/ rising to fill the spots
vacated by the former /i:/ and /u:/ respectively, and so on. That is why
the modern pronouns 'he' and 'she' are written with /e/ (reflecting the
old pronunciation) but pronounced as /i/. In the following chart, the
words are located where their vowel used to be pronounced
-- where they are pronounced today is indicated by the arrows.