Underground Electric Haulage focuses on the locomotives used in modern mine railways. The locomotives of many different types are used for such underground operations as gathering at the loading points, shunting at the pit bottom, hauling man-riding vehicles, but primarily hauling material cars on the main haulage roads of the mine. The locomotives for underground haulage fall into three main groups: (1) compressed-air locomotives, (2) internal-combustion locomotives, and (3) electric locomotives. So far as electric haulage is concerned, the locomotives may be divided into two types: (a) trolley locomotives and (b) storage-battery locomotives. Besides these two main types there are also various combinations, such as trolley locomotives with batteries, cable-reel locomotives with a reel for the automatic unwinding and winding up of the cable, and trolley locomotives fitted additionally with the cable-reel equipment. The book is organized into three parts. Parts I and II discusses trolley locomotives and storage-battery locomotives, respectively, while Part III deals with calculations in mine traction engineering.