L. Frank Baum,
Mary Louise in the Country — XVII. A CLEW AT LAST
(1916)
“ The shadows cast by the towering rocks rendered this place quite dark, so Josie crouched in the deepest shade she could find and listened carefully to the strange sound, trying to determine its origin. It was surely under ground—a little to the right of her—perhaps beneath the hillside, which slanted abruptly from this spot. She decided there must be some secret passage that led to a cave under the hill. Such a cave might be either natural or artificial; in either case she was sure old Cragg used it as a rendezvous or workshop and visited it stealthily on his "wakeful" nights. ”
