When this difficulty has been overcome, and that it will be overcome there can be no manner of doubt, gas engines will rapidly displace the steam engine, because a gas engine with a gas producer, producing gas from any ordinary coal with the same ease as steam is produced from a boiler, will be much safer, and will use one-half the fuel of the very best steam engines for equal power. The first cost also will not be greater than that of steam. The engine itself will be more expensive than a steam engine of equal power, but the gas producer will be less expensive than the boiler at present. Perfect as the gas engine now is, considered as a machine for converting heat into work, the possibility of great development is not yet exhausted. Its economy may be increased two or even three fold; in this lies the brilliant future before it. The steam engine is nearly as perfect as it can be made; it approaches very nearly the possibility of its theory. Its defect does not lie in its mechanism, but in the very properties of water and steam itself. The loss of heat which takes place in converting liquid water into gaseous steam is so great that by far the greater portion of the heat given out by the fuel passes away either in the condenser or the exhaust of a steam engine; but a small proportion of the heat is converted into work. The very best steam engines convert about 11 per cent. of the heat given them into useful work, the remaining 89 per cent. being wasted, principally in the exhaust of the engine. Gas engines now convert 20 per cent. of the heat given to them into work, and very probably will, in a few years more, convert 60 per cent. into useful work. The conclusion, then, is irresistible that, when engineers have gained greater experience with gas engines and gas producers, they will displace steam engines entirely for every use--mills, locomotives, and ships. * * * * * RAPID CONSTRUCTION OF THE CANADIAN PACIFIC RAILWAY. By E.T. ABBOTT, Member of the Engineers' Club of Minnesota. Read December 12, 1884.