The _Argonaut_, as originally built, was thirty-six feet long and nine feet in diameter. She was the first submarine to be operated successfully with an internal-combustion engine. She was propelled with a thirty-horsepower gasolene (petrol) engine driving a single-screw propeller. She was fitted with two toothed driving wheels forward, which were revolved by suitable gearing when navigating on the water-bed. They could be disconnected from this gearing and permitted to revolve freely, propulsion being secured by the screw propeller. A wheel in the rudder enabled her to be steered in any direction when on the bottom. She also had a divers' compartment to enable divers to leave or enter the vessel when submerged, so as to operate on wrecks or to permit inspection of the bottom or to recover shellfish. She also had a lookout compartment in the extreme bow, with a powerful searchlight to light up a pathway in front of her as she moved along over the water-bed. This searchlight I later found of little value except for night work in clear water. In clear water the sunlight would permit of as good vision without the use of the light as with it; while, if the water was not clear, no amount of light would permit of vision through it for any considerable distance. [Illustration: THE "ARGONAUT" AFTER LENGTHENING AND ADDITION OF BUOYANT, SHIP-SHAPED SUPERSTRUCTURE, INCREASING THE SURFACE BUOYANCY OVER 40 PER CENT] As the _Argonaut_ was principally built in order to further test out the possibility of navigating on the water-bed in exploration and commercial work, she was propelled, both when on the surface and submerged, by her gasolene (petrol) engines. Storage batteries were carried only for lighting purposes. The air to run her engines was first drawn into the vessel through a hose extending to a buoy floating on the surface. Later she was fitted with pipe masts, which enabled her to navigate on the bottom in depths up to fifty feet. She functioned satisfactorily from the start. We found we could readily navigate over any kind of bottom, soft or hard, by regulating her buoyancy to suit, and she would, due to her buoyancy, readily climb over any obstruction that did not reach higher than her forefoot. [Illustration: SUBMARINE WITH CUSHIONED BOTTOM WHEELS Showing how such a vessel will surmount a steep declivity while a boat of the diving type (D) will likely "bury her nose" into it or strike with sufficient force to disarrange her machinery. If the submarine has sufficient statical stability she will maintain substantially a level keel even when riding over a steep declivity.]