midnight
In the long , low , narrow chamber , hewn from solid rock , were thirty stalls . Several of them were occupied by spare mules , who turned an inquiring gaze at the visitors , and blinked in the light of their lanterns . At one end were bales of hay and bags of oats , while just outside the door stood a long water-trough , which , as mine water is unfit for use , was supplied from above-ground through iron pipes brought down the slope . In spite of living in a continual midnight , so far from pastures and the light of day , which some of them did not see from one year 's end to another , these mine mules were fat and sleek , and appeared perfectly contented with their lot . Apparently satisfied that justice had been done to his place of abode , Harry Mule offered no further objection to moving on , when they again got into the car , and the stable was quickly left behind . By-and-by Derrick called out `` Door ! '' As it opened for them to pass , and Paul Evert recognized his friend , he cried , `` Oh , Derrick , Socrates -- '' Then seeing the visitors , he stopped abruptly , and stared at them in confusion .