202 Fuel Economy. (April, 
revolutions to be performed than No. 1, and must therefore 
be worth 50 per cent more money. 
Messrs. Johnson and Hobbs, of Manchester, exhibit a 
model of a Patent Apparatus for the Condensation of Smoke, 
Gases, &c. This apparatus is exceedingly simple and 
inexpensive in its construction; it is on the paddle-wheel 
principle, with an addition of projections on the blades to 
produce a finely-divided spray of water, which falls through a 
series of network composed of laths, brushwood, shingle, or 
other material, and is so arranged as may seem best for 
arresting the substances to be operated upon. The same 
liquid may be used over and over again, until charged to any 
extent that may be desired. The inventors declare that this 
machine will be found more effective than the expensive 
condensing towers now used for the purpose, as it produces 
a powerful draught, which can be regulated at will, and the 
solution can be made in the machine as concentrated as may 
be required. The machine has been tried in condensing 
ammonia, and has been found to succeed thoroughly; the 
working parts of the apparatus can be arranged to resist the 
action of hydrochloric and other powerful gases affecting 
metal work. 
Crossley Brothers, of Manchester, exhibit an Atmospheric 
Gas Engine. This engine works as follows :—Gas and air, 
mixed in such proportions as to give a mild explosive com- 
pound, are admitted under a piston which slides air-tight in 
a verticai cylinder open at the top. The compound is 
ignited, explodes, and the explosion drives the piston 
upwards. ‘The ignited gases, having increased in volume, 
lose their heat; their pressure becomes less as the piston 
rises, and when it has got to the top of the cylinder a partial 
vacuum is formed, and the pressure of the atmosphere makes 
the piston descend. The work thus done steadily by the 
atmosphere during the return stroke of the piston yields the 
driving power, which is transferred to the shaft by suitable 
mechanism. This utilisation of the instantaneous power of 
the explosion, by allowing the piston to fly up freely from it 
without doing other work than emptying the cylinder of 
air, is the basis of the economy and success of these 
engines. The sudden energy of an explosion cannot be 
economically applied to push a piston slowly along against 
a load, as in the case of steam-engines; it is thus that 
other gas engines have been superseded by this patent. 
Some of the advantages of this engine, compared with 
steam engines, are that it can be started at a moment’s 
notice, and will at once give out its full power; thus no- 
a 
