The mule was hitched to the car, Derrick sprang in front, cracked the whip that had hung about his neck, and they started on what, to two of them at least, was the most novel ride they had ever undertaken. When they reached his stable Harry Mule stopped short and refused to go on. "What is the matter?" asked Miss Nellie. "I expect he wants us to go in and see his house," answered Derrick. "Why, I never heard of such a funny mule. Do you suppose he knows we are visitors?" "Of course he does," answered the boy, gravely; "and he knows that visitors always want to see the mine stable." So they all went in to look at it. 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. "Never mind, Polly; we'll be back pretty soon," shouted Derrick, as the car rolled on, "and then you can tell us all about it." "What did he say?" inquired Mrs. Halford. "I didn't quite understand," replied Derrick; "but, if you don't mind, we'll go back there after a while and eat our lunch with Polly--he'd be so pleased!--and then we'll ask him." "Who is Polly?" asked Miss Nellie. "He's Paul Evert, my best friend, and he's a cripple." "Oh, he's the boy you saved from the burning breaker! Yes, indeed, mamma, let's go back and eat our lunch with him." Mrs. Halford agreed to this, and after they had visited the blacksmith's shop, where a cheery young fellow named Aleck was installed in Job Taskar's place, they went back to Paul's station. Both the ladies were charmed with the gentle simplicity and quaintness of the crippled lad, and he thought he had never been so happy as in acting the part of host to this underground picnic party. He showed them all the strange and beautiful pictures on the walls of the gangway, and Derrick managed to break off for them a couple of thin scales of slate on which were impressed the delicate outlines of fern leaves.