] I had always been of the understanding that the title "Viscount" was held by the heir of a landowning Lord who, once the Lord was deceased, then attained the title of Lord ____, and subsequently the new Lord's heir then became the Viscount.

] I have just recently read something in which the title Viscount is used to refer to the landowner itself -- as if it were the senior title. I find myself somewhat confused.

To add to Jack's post: I fear that your confusion arises because you've been misinformed. A title had nothing to do with any property ownership. You could have penniless Viscounts and wealthy commoners (as is Mr Darcy). While estates were usually associated with certain titles of nobility, they didn't have to be.