An immense amount of time and money has been expended upon new and ingenious cut-offs for steam engines. Each in its turn, as it was brought before the public, was supposed to excel its predecessors, either in its power of adapting the exact quantity of steam used to the work to be done, or its instantaneous acrion. The best modern engines show, by the indicator cards, between 60 and 90 per cent of the theoretical effect of the steam ; in all cases the figures vary in proportion as care is exercised'in keeping8 the temperature up in the cylinder. All these are improvements, and they tend toward greater economy in the use of steam. Before the steam engine can be called an economical power, our modern system of boilers must be immensely improved, or an entirely new system of applying the heat to the water must be contrived. We all know that the steam engine is at present a most wasteful source of power, and that we realize only between 15 and 25 per cent of the theoretical amount of power derivable from the coal which is consumed. There is about 75 per cent lost somewhere in the boiler, and it seems as if it would be more important to make the vigorous attempts at improvement upon the boiler rather than upon engine. That which Watt did for the steam engine when lie invented the condenser, some engineer of our own time can do by improving the boiler. As it is necessary to apply heat for the generation of steam, and as the boilers of all sea-going steamers must of necessity use salt water, the first improvement should be a better method of abstracting the salt from the water. This is at present performed by the use of surface condensers, but they are large and heavy, and withal do not give perfectly fresh water. This operation should be performed as the water enters the vessel, and before it has passed through the boilers, as in the surface condensation of the present system. As higher pressures and a greater degree of expansion have, so far, proved to be a source of economy, it is probable that we shall see the pressure raised above that which boilers now carry, and as a consequence the steam will be expanded to a greater degree. But before we can arrive at this point, it is necessary that the salt should be extracted from the water before it enters the boiler. What form the boiler may assume is more than any one can say, bat so long as the heat is not applied in a better manner, we must lose a large amount. A large quantity of heat is lost by radiation from all parts of the boiler. It is true we felt the exposed surface, but this is only a method of reducing a loss, whicli with our present form of boiler we must be subject to. Heat is lost as it travels from the furnace to the uptake, indeed some of the currents of heated gases generated in the furnace scarcely reach any of the surface of the boiler at all, but pass through the center of the tubes out through the smoke pipe, having done no work except to fill up spaces which otherwise would have been left vacant, this loss is greater in proportion as the diameter of the tubes or flues are increased. Where all the losses are, it is impossible to state, for it is most difficult to judge at what point heat is being given off in great quantities ; points which we suppose are giving off large amounts may perhaps be wasting but a small percentage of the whole loss. Watt, when he invented the condenser, made, we might well sa,yj the last great improvement m the steam engine. Since his time the boiler has been changed, tubular boilers have been introduced, and the pressure is far higher than any used in his day. No doubt if Watt had been able to get the pressures in his cylinders as great as we now get them, he would have made use of expansion, fully appreciating its benefits. With the low pressures which prevailed, he carried expansion to its most economical limits. As we look back upon the years past, we see that all the improvements of any magnitude have been made upon the boiler; the improvements in the engine having merely kept up to, and followed closely, the ehange in the construction of the boiler. The next great change in the steam engine—the next change that will promote the use of steam and add to its immense utility, will come by improvements in the boiler. We must attack the source of the evil if we wish to overthrow it, and in the faulty construction of the boiler the evil will be found and the difficulty conquered.
This article was originally published with the title "Improvements in the Steam Engine"