“In the first place, it gives more power. You see, three out of every four strokes made by the piston of a gasoline engine--suction-stroke, compression-stroke, and scavenging-stroke--waste power instead of producing it. But the Diesel is what we call a two-cycle engine; its piston makes only two trips for each power-stroke. In the second place, it is cheaper, because instead of gasoline it uses heavy, low-price oil. And this makes it much safer, for the heavy oil does not vaporize so easily. The air in some of the old submarines that used gasoline motors would get so that it was like trying to breathe inside a carburetor, and there was always the chance of a spark from the electric motors exploding the whole business, and your waking up to find the trained nurse changing your bandages. The German navy refused to build a submarine as long as there was nothing better than gasoline to propel it on the surface. They didn’t launch their _U-1_ till 1906, after Dr. Diesel had got his motor into practicable shape. It cost him twenty years of hard work, but without his motor we couldn’t have the modern submarine. And they’re using it more and more in ocean freighters. There’s a line of motor-ships running to-day between Scandinavia and San Francisco, through the Panama Canal. “Aft of the Diesel, here,” continued the engineer, “is our electric motor, for propelling her when submerged. Reverse it and have it driven by the Diesel engine, and the motor serves as a dynamo to generate electricity for charging the batteries. As long as we can get oil and come to the surface to use it, we can never run short of ‘juice.’[14] “Besides turning the propeller, the electricity from the batteries lights the boat, and turns the ventilating fans, works the air-compressor for the torpedo-tubes, drives all the big and little pumps, runs a lot of auxiliary motors that haul up the anchor, turn the rudders, and do other odd jobs, it heats the boat in cold weather--” “And cooks the grub all the year round, don’t forget that, Joe,” said another member of the crew. “Luncheon is served in the palm room.” We ate from a swinging table let down from the ceiling of the main- or living-compartment of the submarine, that extended forward from the engine-room to the tiny officers’ cabin and the torpedo room in the bows. Tiers of canvas bunks folded up against the walls showed where the crew slept when on a cruise. For lunch that day we had bread baked on the mother-ship, butter out of a can, fried ham, fried potatoes, and coffee hot from a little electric stove such as you can see in the kitchenette of a light-housekeeping apartment on shore. The lieutenant’s lunch was carried up to him on the bridge. When the meal was over, most of the men went on deck, and my friend the engineer put a large cigar in his mouth. I took out a box of matches and was about to strike one for his benefit when he stopped me, saying,