the name of which is also found in such forms as Allen and Hellan, lies just west of the Midland Railway, about halfway between Horton and Ribblehead stations, and on the north-east side of Ingleborough. It is one of the most striking and most famous of the Yorkshire potholes, being an elliptical opening in the limestone, 120 ft long and 40 ft wide, with a perpendicular depth of 200 ft. The exploration of it was begun by Mr. Birkbeck of Anley in 1847, who, assisted by Prof. Boyd Dawkins and a large party including three ladies, made a complete examination in 1870.