The _Argonaut_, designed by Mr. Simon Lake, of Baltimore, is a vessel which rolls along the floor of the ocean as a carriage rolls along the highway. In this it differs from any other under-water craft either projected or constructed, for all previous inventors have attempted to navigate their boats between the surface and the bottom. In the invention of this type of submarine boat Mr. Lake elaborated an idea which the United States Patent Office described to be absolutely original, and the _Argonaut_ has undoubtedly done things that no other vessel has before accomplished. Mr. Lake built his first experimental submarine boat, the _Argonaut Junior_, in 1894. After several successful descents she was abandoned, and now lies at Atlantic Highlands, half buried in the sand. Her dimensions were: length, 14 feet, beam 4½ feet, depth 5 feet. _Argonaut No. 2_ was a much bigger boat, and proved that Mr. Lake’s theories were substantially correct. She is 36 feet long. Her diameter amidships is 9 feet; her displacement when entirely submerged is about 59 tons; her draught when at the surface is 10 feet, and when submerged 15 feet. She is built of steel plates ⅜ inch in thickness, and double-riveted over strong steel frames. She is provided with a 30 h.p. “White and Middleton” gasoline engine, which propels her both on the surface and while submerged, and runs all the auxiliary machinery. She has two Mannesmann steel reservoirs for the storage of compressed air, which have been tested to a pressure of 4,000 lbs. per square inch. She is provided with air compressors, water-ballast pumps, and hoisting machinery for raising or lowering her two down-haul weights. She is lighted by incandescent electric lamps throughout, and carries a 4,000 candle-power searchlight in her bows, all run by a dynamo. Machinery for driving her side driving-wheels and various gauges for determining depth, rate of speed and air pressure, are also provided, together with a complete outfit for divers, who are equipped with telephones and electric lamps. The following account of his boat was written by Mr. Simon Lake himself, and we have his permission to reprint it here:— [Illustration: THE “ARGONAUT” IN DRY DOCK. ]