All of us are probably familiar with the notion that the owner of mineral rights may owe some duty of care to support the owner of the fee in his or her surface use of the land. This principle results in a binary system (the surface estate and the right of sup-port) that can be treated easily in tort law. In Pennsylvania the coal companies had owned vast areas of land. The companies had sold much of this land, reserving not only the coal, but "the right to. ..remove the same without incurring in any way liability for any damage to the surface of said lots, or to any buildings or improvements which may be or have been placed thereon." Treating this subject as a part of tort law, most of us in this day and age would discard this reservation, invoking some words about unconscionability or public policy. In Pennsylvania, however, the court treated this reservation within the subject matter of property law.This reservation became known as the "third estate" because the Pennsylvania court recognized that "three estates may exist inland, the surface, the coal and the right of support, and that each of these may be vested in different persons at the same time.''This peculiar trinitarian approach was to have some practical consequences.
E. F. Roberts,
Mining with Mr. Justice Holmes,
39 Vanderbilt Law Review
Available at: https://scholarship.law.vanderbilt.edu/vlr/vol39/iss2/4