All About Engines

 x98 All About Engines temperature. The gas, which was formerly allowed to escape freely from the top of the furnace, con- tains rather more than 30 per cent.—chiefly carbon monoxide—which is combustible, and at night the blaze could be seen for miles around. It was sug- gested by the late Mr. B. H. Thwaite in 1892 that this waste should be prevented, and the gas used in gas engines. For every ton of coal charged into the furnace more than 120,000 cubic feet of gas is pro- duced, and, taking the whole country, there is suffi- cient energy to yield 750,000 horse-power continu- ously all the year round. Three years later, in 1895, the Glasgow Iron Company adopted the sugges- tion, and their example was followed by many other firms, especially in Germany and the United States. The Growth of the Gas Engine When, after 1889, cheaper gas became available the problem of the large engine arose. There were two principal difficulties. One lay in constructing the cylinder, and the other in keeping the piston cool. The gas engine cylinder is rather a compli- cated casting, and owing to explosions inside and cooling water outside great strains are set up, so that it is liable to crack. The difference of temperature of two points an inch apart may be 50°, and even though iron has not a high rate of expansion, this difference between points so near together sets up very severe strain. Engines giving 1,000 horse-power for one cylinder have been made, but they are not