Now we put the booster on--that little miniature locomotive for the trailing-wheels that we saw a few minutes ago, built like an automobile engine and having the same gritty driving power. When the engineer comes to that nasty hill, in goes the booster and up goes the 3000-ton train over the hill, just as easily apparently as if it were coasting on a down-grade. The most famous passenger-train to-day in America, if not indeed in the whole world, is the Twentieth Century Limited, running between New York and Chicago, 969 miles in a flat twenty hours. It began twenty years ago as a single train of moderate length--about seven or eight Pullman cars and a diner. To-day it almost always consists of at least two sections, each of ten to twelve heavy steel diners and Pullman sleepers. In figures, the weight increase is close to 216 per cent. The train easily might make the run through to Chicago in eighteen hours as it did at the outset if safety and other conditions permitted. The energy of the locomotive is not the limiting factor. Now how has this been done? How has the typical locomotive of the Twentieth Century been so improved as to keep the train that it hauls up in the top notch of American passenger carriers? The answer is easy: by the constant application of every proved device for the improvement of that machine. The New York Central, which operates this train, does not often stand convicted of a lack of mechanical progress. Come to figures, once again: A certain well-known railroad, which is thoroughly sold on the idea of the improved locomotive, in the last twenty-five years has steadily increased its average tonnage per train by from 400 to 1700 tons over the old-time figures. Its maximum is now close to 3200 revenue tons. In this same quarter of a century this railroad shows 233 per cent. increase in the weight of the train and 66 per cent. increase in the average speed. To-day it thinks nothing of hauling a 5000-ton train at a steady rate, uphill and down dale, of twenty-five miles an hour. Our steam locomotive is a laggard? Only when you do not give it a fair opportunity to show its real worth. * * * * * If all our other railroads were as progressive in this as the two that I have just instanced, there would be no reason for this detailed attention to the problem. Unfortunately they are not. A moment ago I said that two things had held back the development of our steam locomotive--tradition and cost. Have I not now settled the question of cost, as far at least as it may be settled in these pages, by showing the great economies to be effected in the use of an efficient engine--economies, roughly speaking, averaging 25 per cent. in the operation of the locomotive? Now come to the problem of tradition.