In 1740 John Colvil bought out Cocke and his colleagues and, writes Fairfax Harrison "many lesser men and by pre-arrangement divided the territory with William Fairfax. Keeping for himself the lands lying between Catoctin Creek and the Catoctin Ridge and stretching from the Potomac to Waterford, he conveyed to William Fairfax 46,466 acres, constituting all the territory on the Potomac lying between Catoctin Creek and the Shenandoah River, including the Blue Ridge from Gregory's Gap to Harper's Ferry. The purchaser divided the property at the Short Hills into two estates, naming the northern one 'Shannondale' and the southern one 'Piedmont' and administered them as manors, on leases for three lives. By his will he left these lands, with his mansion house, Belvoir, to his eldest son, and the latter in turn, by his will of 1780, entailed them, with the intention that they should constitute the 'plantation' of Belvoir House, always to be held with it. But soon after this last will was written, the success of the American Revolution made it necessary for George William Fairfax, by codicil, to change his testamentary dispositions and his proposed entail was never made effective."[48] [48] _Landmarks of Old Prince William_, 273. After Colvil had settled with William Fairfax, he still held 16,290 acres along Catoctin Creek, to say nothing of 1,500 acres on Difficult Run, his plantation on Great Hunting Creek known as Cleesh and other lands in the Northern Neck. Born at Newcastle-on-Tyne, he was closely related to the Earl of Tankerville, through the latter's mother being his first cousin--a matter in which he took some pride and which was to be of even more moment to the Earl; for when Colvil came to make his will in 1755, he left his plantation Cleesh, then containing about 1,000 acres, to his own brother, Thomas Colvil, for life with remainder over "to the Right Honourable the present Earl of Tankerville and his heirs forever" and also "in consideration of my relation and alliance to the said Earl of Tankerville son of my father's brother's daughter," he left to him outright his 16,000 acres of land on the Catoctin, his 1,500 acres on Difficult and his interest in a certain nearby copper mine.[49] Thenceforth these lands remained in the Earl's family until after the Revolution. Thus originated the Earl of Tankerville's title to certain Loudoun lands, reference to which occasionally yet is heard. [49] The will is on record in Fairfax County. About 1739 Josias Clapham, of an ancient family of Yorkshire (which long has been associated with the Fairfaxes there) bought land near the Point of Rocks and before his death owned much land in the Northern Neck. He died sometime prior to the 27th December, 1749, when his will, dated the 29th October, 1744, was proven in Fairfax County. In that will he left