MECHANICS AND USEFUL ARTS. 87 



made of boiler iron plates, united together in the most perfect manner, 

 and rendered perfectly air and water tight. The after part is occu- 

 pied as the cabin, and is lighted by means of a number of " bulls' 

 eyes." The cabin is capable of accommodating eight or ten persons 

 with ease. The forward compartment is used as an air and water 

 chamber. The length of the whole machine is 30 feet, diameter 1 

 feet. The principle upon which it operates is somewhat similar to the 

 diving-bell, though the manner in which the occupants of the cabin 

 are supplied with fresh air, and enabled to remain for a long time 

 under water, is exceedingly ingenious, air-pipes extending to the sur- 

 face not being employed. The interior is divided into compartments. 

 The place which the submarine explorers occupy is about two fifths of 

 the vessel ; in the other part are two large reservoirs, all made of plate- 

 iron, into which are fitted two pairs of pumps, having different func- 

 tions, either for air or water. The object of the duplicating pumps is 

 to guard against those accidents which might render one unserviceable. 

 Each pump has four cocks to produce alternately the expansion and 

 compression of the air, and the expulsion or supply of water, in such a 

 manner that they may throw off or compress a supply of air or water, 

 at pleasure, to the reservoir spoken, of inside. The whole operation of 

 this vessel depends upon the displacement of a certain quantity of con- 

 densed air, and in taking in or throwing off a body of water, more or 

 less, by working the pumps. Thus, if it is desired to descend from the 

 surface, the crew, before closing the top man-hole, (man-holes being 

 placed both at the top and bottom of the machine,) will force into the 

 air-reservoir the supply of air necessary to balance the weight of the 

 column of water, proportioned to the depth it is desired to descend ; 

 the deeper the descent, the more air is condensed in the reservoir ; this 

 prevents the water from coming in below, according to the laws of 

 equilibrium of fluids. Having obtained a sufficient supply of air, the 

 man-hole above is closed, and the submersion of the vessel effected, bv 



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using pumps to pump water into the water-reservoir. When the vessel 

 has arrived at the bottom, the lower man-holes are opened, and explora- 

 tions made at convenience. A valve communicates with the air-reser- 

 voir and the apartment of the operators. When it is desired to ascend 

 to the surface, the lower man-holes are closed, and the water, which 

 was before pumped in, is expelled. The operations of ascending and 

 descending are thus performed with great rapidity ; but for the pur- 

 pose of guarding against the possibility of accidents, another plan is 

 arranged on the outside of the vessel. Upon each side is placed a 

 strong metallic platform, or shelf, loaded with ballast. These shelves 

 are connected with a lever in the cabin, and, in case of accident, can 

 be made to fall, dislodging the ballast and instantly sending the vessel 

 to the surface. The vessel can thus descend safely to any depth, from 

 10 to 100 feet, without direct or indirect communication with the 

 exterior. This is altogether the reverse of the diving-bell, which 

 receives its air always through a tube from the surface of the water. 

 It is calculated that from three to seven men can remain in the vessel 

 for seven hours. It is also proposed to purify the air of the cabin from 

 the carbonic acid generated in respiration, by forcing it, by means of a 



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