Inside they found themselves in a compartment much resembling the wheelhouse of an ordinary surface craft, except that there were various instruments to show submergence, and the quality and pressure of the air, and devices for handling the engines; for one of the features of Mr. Barr's invention was that it could be handled by one man once the engines were going. Leaving the conning tower, they descended a steel ladder into the heart of the submarine. The centre was occupied by a comfortably fitted-up room which contained, among other things, a small library and a phonograph. The inventor switched on a button and the "cabin," as it may be called, was instantaneously flooded with a soft light, bright but not glaring. In the bulkheads at either end of this compartment were doors, steel riveted and solid looking. The inventor explained that beyond the stern one were located the engine room and crew's quarters, while on the other side of the forward portal lay the sleeping quarters, galley or kitchen, and bathroom. Beyond these again came the torpedo room, which contained the machinery for launching the death-dealers. Each of these was inspected in turn, the boys being delighted with the compactness and neatness of everything. "Now," said the inventor, "we will visit the engine room." Paul Perkins and Hiram looked interested; machinery was one of their hobbies. The _Peacemaker_ carried two sets of engines, electrical for running under the surface, and gasoline for use above water. The engines were fitted tandem-wise, and to their shafts were attached twin screws of a novel design that gave great speed and controlled the submarine easily. The gasoline engines were of fifteen hundred horse-power each, and the electrical had a trifle lower capacity. In the engine room, too, were the powerful pumps used for emptying or filling the submarine's submergence tanks as it was desired to rise or descend. Aft of the engine room came the gasoline tanks, the storage batteries, and some minor machinery, such as an ice-making plant, air compressor, and so on. In the engine room, too, was a comfortable upholstered lounge for the engineer on duty to rest upon. Several dials and gauges were on the walls of this compartment, enabling the engineer to know at all times under just what conditions the submarine was proceeding. It was in the engines themselves that the inventor had excelled all other types of submarines, as well as in the peculiar attributes of the hull. Extra tanks were provided whereby, in the event of the main supply of gasoline giving out at any time, the _Peacemaker_ could be run quite a distance on those alone. "How long could you stay below the surface?" asked Rob, as they came back into the main cabin once more. There they took their seats on broad leather divans which at night time could be converted into beds or bunks by pulling a lever which caused them to turn over and reveal a snug resting place.