From cast-iron wheels and old rails, however, the percentage is much larger, for while at present new passenger car-wheels of this class, weighing about five hundred and fifty pounds, are worth about ten dollars each, they will bring in the market, when worn out after running say fifty thousand miles, about twenty dollars per ton. Four wheels go to the ton, which represents five dollars per wheel, or fifty per cent. of the original cost. With old rails the percentage is even higher, in the present condition of the rail market. Old iron rails are worth within four or five dollars of the price of new steel, and the old steel about seventy per cent. of the price of the new. These high percentages assist in making up for the materials which are entirely consumed in the service, and which never form a part of the ordinary scrap-heap, such as oils, waste, and paints. While the majority of general supplies just mentioned briefly may be arranged for as required and purchased from month to month upon regular requisitions, there are certain staple articles which are provided for in advance by contract. Among them principally are the engine-coal, rails and ties, stationery, passage-tickets, and time-tables. More money is expended for such supplies than for any others, and contracts with responsible business houses, for their delivery at fixed prices for the limit of at least a year, are generally made to insure, in the first place, the lowest market rates and, again, to make the delivery certain. Locomotive fuel is the largest single item of expense in the operation of any road, the consumption of it running up as high as a million tons per annum on some large roads; and while there are a few exceptional cases where wood is used as fuel, coal is the necessary element in nearly every case in America to-day. Of the two general varieties--bituminous or soft, and anthracite or hard--it is safe to say that bituminous coal is the more economical, assuming that the grade employed is the best, this economy lying both in the original cost and the fact that the bulk of it goes to serve its purpose, there being comparatively little waste in the way of ashes; while the anthracite produces many ashes and clinkers, requires much more care and attention on the part of the stoker or fireman, and costs, as a general rule, about thirty per cent. more. Economy, however, should not be carried too far in any branch of the service, and if the passenger traffic be heavy the use of soft coal may be a great detriment. To a traveller there can be nothing more disagreeable than the smoke and cinders emanating from it; and if, besides this, the road be an especially dusty one, the combination of dust, smoke, and cinders will be quite sufficient to turn the tide of travel in some other direction and over another route.