The brick arch in the fire-box: A sort of second cousin to the superheater. Its name to a large degree indicates its nature. An arch thrown across the forward end of the fire-box has a very marked tendency to insure complete combustion of the fuel before the heat reaches the flue-tubes of the boiler and hence achieves a great economy in coal or oil consumption. Its use came with the development of the maximum width of the fire-box in the newest types of American locomotives, which in turn was accomplished when the locomotive had been lengthened and a pair of trailing-wheels placed just back of its drivers. The feed-water heater: An allied device for quickening the production of boiler steam and so effecting a further economy in coal consumption. Perhaps the least tried and so the least established of all these devices. The booster: In reality a miniature locomotive, attached to those two trailer-wheels just back of the drivers and giving to the biggest locomotive at its starting-point or other points of real stress the accelerating power equal to that which 50,000 more pounds of additional locomotive would be able to give. Yet the booster is as ingeniously geared from its cylinders to its driving power as the engine of a high-grade automobile and weighs but 3500 pounds all told--a mere nothing in comparison with the energy that it gives off. Its application and disconnection are almost automatic. The engineer, when he is in need of its assistance either at starting or upon a steep grade, puts its additional power into play by a quick twist of a tiny lever at his side. "Humph," interrupted my friend the old railroader out in the West, "I suppose you think that we are going to get engineers of the caliber to handle all these fancy claptraps that you would put upon the engines?"