I got into a discussion with a coworker yesterday about the semi-colon.
He had asked me to double check a letter he was writing to an elected official.
I said, "I don't think you should use a comma here. Use a semi-colon or else make it two sentences."
I couldn't give an eloquent reason for the use of the semi-colon other than I recalled "The Elements of Style" by Strunk and Wagnalls. He had no idea what I was talking about. Maybe being 17 years younger than me has something to do with it.
Anyways, turns out the guide by Strunk and White (hey I was pretty close) turned 50.
For all intensive purposes, this is worth a read: