midnight
But Duncan 's work there had only begun . Having solved the problem of shipping coal as fast as the miners could dig it , he gave his attention next to the equally pressing problem of increasing output . In the solution of that a great help unexpectedly came to him . He was sitting late one night over the books and correspondence , when , near midnight , a miner sought speech with him . He bade the man enter and , without looking up from the papers he was studying , asked him to take a seat . Still without taking his eyes from the papers , he presently asked of the man , who had not accepted the invitation to sit : `` Well , sir , what can I do for you ? '' `` Nothing , '' answered the man .