The vessel _Le Plongeur_ carried a detachable boat, and Captain Hovgaard in his design also supplied such a boat. It was made to stand the same pressure as the submarine itself, and rested on a saddle-shaped packing, against which it was tightly pressed down by means of a number of clips. Inside the packing was a circular door in the boat and a corresponding and smaller one in the ship arranged in such a way that it was possible to get up into the boat, close the lower lid in the ship, and then the lid in the boat. This done, all the handles of the clips were turned and the water would probably enter the space inside the packing, and if not it might be made to do so through a small pipe leading from the outside to the space, and provided with a stopcock. The boat would now have a certain buoyancy, but would hang on in two main clips, placed one at each end of the detachable boat on mechanical connection with each other so that they could only be let go both at the same time, thereby preventing jamming. When these clips were opened the boat would ascend to the surface; communication with the vessel, if somebody should be left behind, might be kept up by telephonic connection. M. Goubet, M. Drzewiecki, and other inventors provided their vessels with means for being propelled by the crew, working either oars or pedals, in the event of the machinery failing to act. Respiration, or breathing, is a part of the life of all organisms, whether animal or vegetable. Air is taken into the lungs; the oxygen is absorbed, while the carbonic acid is given back again to the atmosphere. The respiration of human beings or animals in closed chambers to which the air is denied access is not possible beyond a certain period. The oxygen is sooner or later, according to the size of the chamber, used up, and the air becomes so vitiated with the carbonic acid expelled by the lungs that the vital functions of the body are arrested. Many of the earlier submarine boats carried no reserve of air, as the time that they were intended to remain under water was not long. Reference is made in old writings to the “chymicall liquor” supposed to have been used by Cornelius Drebbel to restore the purity of the air in his under-water vessel, but what its composition was we shall never know. The air required for respiration in a submarine vessel may be supplied in two ways. 1. By some chemical method which purifies and regenerates the vitiated air. 2. By compressed air or oxygen carried in special reservoirs. 3. By pipes leading down from the surface to the submerged vessel through which fresh air is drawn and the foul air expelled. 4. By the return of the boat to the surface and the taking in of a fresh supply of air.