MECHANICS AND USEFUL ARTS. 9 



plished by a new principle, which he calls " the regenerative princi- 

 ple of condensation." The regenerative condenser, as applied to a 

 high-pressure engine, consists of an upright rectangular trunk of cast- 

 iron, the lower end of which assumes the form of a cylinder, and con- 

 tains a working piston. The trunk itself contains a set of copper or 

 brass plates, placed upright and parallel to each other, with a space 

 between them of the same breadth as the plates, or from one twelfth to 

 one sixteenth of an inch. The upper end of the condenser communi- 

 cates on one side with the exhaust part of the engine, and on the other 

 with a hot well through an uncovering valve. The plates are fas- 

 tened together ^by thin bolts, with washers to keep them apart. Di- 

 rectly below the plates a cold-water jet enters the condenser, whose 

 action is as follows : Motion is given to the piston by the engine, 

 causing it to effect two strokes for every one of the engine. At the 

 moment the exhaust part of the engine opens, the plates are com- 

 pletely immersed in water, a small portion of which has entered the 

 passage above the plates, and is, together with the air present, car- 

 ried off by the rush of steam through the valve into the hot well, 

 where the water remains while the excess of steam proceeds into the 

 atmosphere. An instant later the water recedes between the plates, 

 exposing first their edges to the steam, which condenses thereon, and, 

 being still of atmospheric pressure, heats them to nearly 212 F. But, 

 in proportion as the remaining steam becomes expanded, additional and 

 colder portions of the plates are exposed by the receding water. At 

 the time the water-level sinks below the plates, the greater portion 

 of the steam is condensed, its lateral parts being deposited in the 

 plates, which are heated at their upper ends to 210, and at the lower 

 to about 140. The remaining steam is thereupon condensed by the 

 cold jet. The communication is completed before the working piston 

 has accomplished one seventh part of its stroke. In reascending, to- 

 wards the end of the stroke the water absorbs the heat from the plates 

 in the same successive manner, and issues into the upper passage 

 nearly boiling hot, when it meets with the succeeding discharge of 

 the cylinder, and is carried off into the hot well, as described. The 

 advantages obtained by this condenser are the allowing a portion of 

 the steam to escape uncondensed, and the condensing the rest with a 

 minimum of condensing water. The escaping steam may be used to 

 create a draught in the chimney, and the hot water partially to sup- 

 ply the boiler, thus saving ten per cent, of the fuel. No power is ab- 

 stracted from the engine ; it is cheaper and more compact than other 

 condensers, and is easily attached to low or high-pressure engines. 

 Mr. Robert Stephenson strongly commended the invention, but doubted 

 its applicability to locomotive engines. London Mining Journal, 

 May 19. 



PIRSSON'S FRESH-WATER CONDENSER. 



AT the meeting of the Franklin Institution, May 17, Mr. B. H. 

 Bartol made some interesting remarks in relation to Pirsson's fresh- 

 water condenser, now in use on board the steamer Osprey. The pecu- 



