Following the periods of hand operation and then pony haulage, a pair of steam locomotives were delivered from Stephen Lewin of Poole in 1877. "Ant" and "Bee" were 0-4-0 tank locomotives made unusually narrow, in order to fit within the adit. They were 4 ft 9in high and only 3 ft wide. Their two 4×6in inside cylinders had Bagnall-Price valve gear and a geared drive to the rear axle, but coupling rods between the axles. The arrangement of the water tanks was particularly unusual, being a front tank ahead of the smokebox, in order to reduce width. The boilers were launch-type, as were commonly used for small locomotives with insufficient space between the frames for a conventional firebox.