I happened to read J.S.Mill's writing, and found "an unversity" used in it, instead of "a university". I think "a university" is the right choice in the present-day English, but why did Mill use the phrase "an university", not "a university", in his text? Maybe, the English that was used when Mill was alive has a different rule regarding the article usage?
I'd appreciate it if you would answer my question.
What is special to an university on these subjects belongs chiefly, like the rest of Sits work, to the intellectual department.
An university exists for the purpose of laying open to each succeeding generation, as far as the conditions of the case admit, the accumulated treasure of the thoughts of mankind.
These sentences are quated from Inaugural address delivered to the University of St. Andrews by J.S.Mill.