In summer he is expert with the "track jacks" and constantly putting in bits of ballast here and there; and in the winter, when the frost and snow have made it impossible to touch the ballast, he keeps his elevations by means of "shims." A "shim" is a piece of wood, from shingle thickness to the width of two ties piled one upon the other, and is wedged between the tie and the rail till summer comes and the line can be corrected by ballasting. The section-boss must keep pace with a job that is no sinecure. If his gang, in eagerness to be on dress parade, almost throws dirt on the rear steps of the boss's private car as it goes whizzing down the line, he must also see to it that they keep plugging at it where there is not even a locomotive whistle within sound. He must be thrifty, economical. He must remember that the humble cross-tie which once cost a quarter now costs almost a dollar, and that for one of these to be found neglected in the ditch is almost a capital crime. He must have an eye for loose spikes and angle-plates, for the big boss has hinted at the annual loss to the road in these simple factors. At his call and that of the superintendent of bridges and buildings is a work-train, made up of a few flat-cars and discarded coaches, doing boarding-house Pullman service in their declining years, which looks after work too sizable for the section-boss and his little gang, and yet not large enough for the attention of the dignified gentlemen who are known as the reconstruction engineers. Yet some of the feats of these work-train gangs have the crackle of engineering genius. It takes brains to rip out a little timber span and replace it in the interval between two trains spaced a couple of hours apart, and in the railroad, brain work often comes from the shabby workman, from the man who graduates from the command of his own battered hand-car. * * * * * All this elaborate system of railroad operation has been built up through many years of practice. Experience has been more than a teacher in the business, which becomes yearly more and more nearly a developed science; she has been a whole faculty and a curriculum, too. Methods that promised well at the outset have been found faulty after trial, and rejected. Committees of trained experts have pondered and reported voluminously; the standard railroad codes of every sort have been born because of them. The operation of the railroad has been brought close to science. It would seem as if the entire field had been completely covered.