The pumping engine for use in mines was a great success. In 1782 the firm sought to modify Watt's invention so that the engine had a rotary motion, making it suitable for use in mills and factories. On a 1781 visit to Wales Boulton had seen a powerful copper-rolling mill driven by water, and when told it was often inoperable in the summer due to drought suggested that a steam engine would remedy that defect. Boulton wrote to Watt urging the modification of the engine, warning that they were reaching the limits of the pumping engine market: "There is no other Cornwall to be found, and the most likely line for increasing the consumption of our engines is the application of them to mills, which is certainly an extensive field." Watt spent much of 1782 on the modification project, and though he was concerned that few orders would result, completed it at the end of the year. One order was received in 1782, and several others from mills and breweries soon after. George III toured the Whitbread brewery in London, and was impressed by the engine there (now preserved at the Powerhouse Museum, Sydney, Australia). As a demonstration, Boulton used two engines to grind wheat at the rate of 150 bushels per hour in his new Albion Mill in London. While the mill was not financially successful, according to historian Jenny Uglow it served as a "publicity stunt "par excellence"" for the firm's latest innovation. Before its 1791 destruction by fire, the mill's fame, according to early historian Samuel Smiles, "spread far and wide", and orders for rotative engines poured in not only from Britain but from the United States and the West Indies.