After receiving the patent, Watt did little to develop the engine into a marketable invention, turning to other work. In 1772, Watt's partner, Dr. John Roebuck, ran into financial difficulties, and Boulton, to whom he owed £1,200, accepted his two-thirds share in Watt's patent as satisfaction of the debt. Boulton's partner Fothergill refused to have any part in the speculation, and accepted cash for his share. Boulton's share was worth little without Watt's efforts to improve his invention. At the time, the principal use of steam engines was to pump water out of mines. The engine commonly in use was the Newcomen steam engine, which consumed large amounts of coal and, as mines became deeper, proved incapable of keeping them clear of water. Watt's work was well known, and a number of mines that needed engines put off purchasing them in the hope that Watt would soon market his invention.