All About Engines

332 All About Engines half the rate. We are exhausting our supplies more rapidly than any other country in Europe. But there are other methods of economising, even in the production of power. Where large engines are impossible and electricity cannot easily be obtained, it is more economical to convert coal into gas in a gas producer, and to use the gas in gas engines than to burn coal under a boiler. It has not hitherto been possible to make gas engines large enough to com- pete with steam turbines for large powers, and for generating electricity they are not quite so suitable, but for all other purposes up to 1,000 horse-power they are effective and economical. Moreover, the bye-products which can be collected from the pro- ducer are valuable in industry and agriculture, so that a double purpose is served by their use. The advantage of the gas engine, as an engine, lies mainly in the following facts :— (a) The heat is produced in the cylinder, just where it is converted into work. There is no loss, therefore, by radiation from the surface of boilers and long lengths of piping. (b) When air and gas are mixed in proper proportions the combustion is rapid and perfect. There are no unburnt particles like those which pour out of the tops of factory chimneys, which not only represent waste in a direct sense, but lead to an unnecessary expenditure of soap and water, and cast a black pall over every manu- facturing town.