The professor's volubility knew no bounds;
Volubility is a rare word, meaning "ability to talk for a long time", and if it "knew no bounds", we mean (by personification) that he was able to talk forever, or a very long time. This is hyperbole. It isn't really true that he could talk forever!
he could talk through a hurricane
This is more hyperbole. It would difficult to talk in a hurricane, but it claims that the professor could do this anyway. Really it means "The professor could talk, even when other people would find it difficult".
elaborate a point
When you are talking, you make "points" These are the facts that you claim. If you add details to the points, you "elaborate the point".
from one St. Patrick's day to the next.
Ie. for one year. This is hyperbolic, but it means he could "elaborate a point" for a very long time. The use of St Patrick is due to this being an Irish text.