help with a/an

I'm a native English speaker, but I was wondering if anyone had an answer for this... Here's a quote from Thomas Jefferson:

"There is not a young man now living in the United States who will not die AN UNITARIAN."

Now, the 'u' in 'unitarian' is pronounced /ju/ so it should be "a unitarian" because "an" is used only before vowels, not semivowels...

So my question is, at the time of this statement (1822) was the /ju/ still pronounced /u/ or is this a form of hypercorrection?

Don't know, but I believe the exact usage has varied. I remember reading that you can use "an" before an h-sound. I don't do that, but the practice has varied, I think.

>><<So my question is, at the time of this statement (1822) was the /ju/ still pronounced /u/ or is this a form of hypercorrection?>>

Most words where <u> is now /ju:/ had a diphthong /Iu/ at one point, so I suppose 'an Unitarian' /@n IunIte:r\i:@n/ works better than /@n ju: .../. Here's what Wells has to say: "In London the falling diphthong [Iu] had by the end of the seventeenth century given way to the rising diphthong [ju:]..." It's possible though that [Iu] survived longer in the US. <<

Mind you also that there are English dialects in which such a shift never occurred, and rather other shifts occurred. I know that there are Welsh English dialects, for instance, which did not shift [Iu] to [ju:] but rather to [i:w], and I think I may have heard about such a thing in some southern NAE dialects (I am not certain about that one).

Thanks ya'll... The [Iu] theory sounds good enough for me.