During the half-century following the death of Fulton, scarcely a year went by without the designing or launching of a new man-power submarine. Some of these boats, notably those of the Bavarian Wilhelm Bauer, were surprisingly good, others were most amazingly bad, but none of them led to anything better. Inventor after inventor wasted his substance discovering what Van Drebel, Bushnell, and Fulton had known before him, only to die and have the same facts painfully rediscovered by some one on the other side of the earth. A striking example of this lack of progress is Halstead’s _Intelligent Whale_. Built for the United States navy at New York, in the winter of 1864-5, this craft is no more modern and much less efficient than Fulton’s _Nautilus_ of 1801. The _Intelligent Whale_ is a fat, cigar-shaped, iron vessel propelled by a screw cranked by manpower and submerged by dropping two heavy anchors to the bottom and then warping the boat down to any desired depth. A diver can then emerge from a door in the submarine’s bottom, to place a mine under a hostile ship. It was not until 1872 that the _Intelligent Whale_ was sent on a trial trip in Newark Bay. Manned by an utterly inexperienced and very nervous crew, the clumsy submarine got entirely out of control and had to be hauled up by a cable that had been thoughtfully attached to her before she went down. Fortunately no lives had been lost, but the wildest stories were told and printed, till the imaginary death-roll ran up to forty-nine. The _Intelligent Whale_ was hauled up on dry land and can still be seen on exhibition at the corner of Third Street and Perry Avenue in the Brooklyn Navy Yard. Lack of motive-power was the reason why man-sized submarines lagged behind their little automatic brethren, the Whitehead torpedoes. Compressed air was just the thing for a spurt, but when two Frenchmen, Captain Bourgois and M. Brun, built the _Plongeur_, a steel submarine 146 feet long and 12 feet in diameter, at Rochefort in 1863, and fitted it with an eighty-horse-power, compressed-air engine, they discovered that the storage-flasks emptied themselves too quickly to permit a voyage of any length. The _Plongeur_ also proved that while you can sink a boat to the bottom by filling her ballast-tanks or make her rise to the surface by emptying them, you cannot make her float suspended between two bodies of water except by holding her there by some mechanical means. Without anything of the kind, the _Plongeur_ kept bouncing up and down like a rubber ball. Once her inventors navigated her horizontally for some distance, only to find that she had been sliding on her stomach along the soft muddy bottom of a canal. Better results were obtained after the _Plongeur_ was fitted with a crude pair of diving-planes. But the inefficiency of her compressed-air engine caused her to be condemned and turned into a water tank. [Illustration: The _Intelligent Whale_. Drawn by Lieutenant F. M. Barber, U. S. N., in 1875.]