The county of Cornwall was a major market for the firm's engines. It was mineral-rich and had many mines. However, the special problems for mining there, including local rivalries and high prices for coal, which had to be imported from Wales, forced Watt and later Boulton to spend several months a year in Cornwall overseeing installations and resolving problems with the mineowners. In 1779 the firm hired engineer William Murdoch, who was able to take over the management of most of the on-site installation problems, allowing Watt and Boulton to remain in Birmingham.