At another time we were operating alongside of a wreck in which we were demonstrating the practicability of removing cargo from the sunken wreck to a small experimental cargo or freight-carrying submarine. This freight-carrying submarine was practically a tank, and was built purely for demonstrating purposes. It was nine feet in diameter and twenty-five feet long, with conical ends (see illustration, page 278). It had wheels underneath so that it could be towed on the bottom by the _Argonaut_. The _Argonaut_ had gone down alongside of a sunken wreck loaded with coal, with the freight submarine alongside opposite to the wreck. The _Argonaut_ had a centrifugal wrecking pump mounted on her deck, driven by a shaft extending through a stuffing box, and to fill the little cargo-carrying submarine it was necessary for the diver only to place the suction pipe connected with the wrecking pump into the sunken coal barge and the discharge pipe into the hatch of the cargo submarine, start the pump, and transfer the coal from the sunken wreck to the cargo-carrying submarine. We made several successful demonstrations of this, and actually transferred fifteen tons of coal from the sunken wreck to the cargo submarine with a six-inch pump in nine minutes. It was then necessary for the diver only to close the hatch of the freight-carrying submarine, admitting compressed air into the interior which blew the water out through check valves in the bottom of the freight submarine, and then the freight submarine would come to the surface with her cargo, which could be towed into port on the surface by surface tugboats. One day, when down on the bottom repeating this experiment, the diver came back into the diving compartment and said that he wanted the _Argonaut_ moved ahead about twenty feet. The divers, having become familiar with the operation at this time, were a little careless. There were three of us in the diving compartment at the time, and it was "up to me" to go back into the machinery compartment and move the boat forward twenty feet; we could tell the distance by the revolutions of her wheels over the bottom. I told them to close the bottom diving door, and when I left the diving compartment they were in the act of doing so. As I looked back through the lookout window in the air-lock door I saw that the diver had taken off his helmet and was smoking his pipe--this being the first thing a diver always wants to do when coming out of the water. I then started to move the boat, assuming that the diving door was closed, but the boat did not move. Having been at rest there for some time, I assumed that she had probably taken in through a leaky valve some additional water, and I decided that it was necessary to lighten her somewhat, so I called on the telephone and asked them if everything was all right in the diving compartment and they replied that it was. I then pumped and tried her again; still she did not move, so I pumped out a little