midnight
Not many even of the inhabitants of a manufacturing town know the vast machinery of system by which the bodies of workmen are governed , that goes on unceasingly from year to year . The hands of each mill are divided into watches that relieve each other as regularly as the sentinels of an army . By night and day the work goes on , the unsleeping engines groan and shriek , the fiery pools of metal boil and surge . Only for a day in the week , in half-courtesy to public censure , the fires are partially veiled ; but as soon as the clock strikes midnight , the great furnaces break forth with renewed fury , the clamor begins with fresh , breathless vigor , the engines sob and shriek like `` gods in pain . '' As Deborah hurried down through the heavy rain , the noise of these thousand engines sounded through the sleep and shadow of the city like far-off thunder . The mill to which she was going lay on the river , a mile below the city-limits . It was far , and she was weak , aching from standing twelve hours at the spools .