Exactly the same principles are involved in this matter as in the case of a thrifty proprietor of a country-store, whose profits each year depend materially upon the closeness and care with which his stock in trade is purchased from the wholesale dealers in a large city. A purchasing agent's experience is varied in the extreme, dealing as he does with all classes of salesmen and business houses. There is no end to the operations which skilful salesmen go through in offering their stock; but after some experience a sharp buyer will be able to fortify himself against the best of them--even against the clever vender of varnishes who disposed of one hundred barrels of his wares in small lots to different buyers, on a sample of maple-sirup. On the other hand, a salesman who, when a buyer asked him if his oil gummed, replied that "it gummed beautifully," lost the chance of ever selling any goods in that quarter. As has been said, the ordinary or general supplies consumed in the operation of the average railroad include almost everything known to trade. Tobacco, for the gratification of the taste of a gang of men out on the road with the snow-plough, is not outside the list; and even pianos, for some trains (since the days of absolute comfort and possible extravagance have begun) for the benefit of passengers setting out on long journeys; nor do we lose sight of books, bath-tubs, and barbers. The practical feature involved, however, calls for an endless variety of expensive as well as inexpensive materials. It is a safe rule to follow that anything which goes into the construction either of track, equipment, or buildings, should be the best. Care should always be exercised against the use of any material the failure of which might be the cause of loss of life, and consequently result in heavy damages to the company. Iron alone enters so extensively into railroad construction and operation that it is safe to say three-fourths of all manufactured in this country is consumed directly or indirectly in this way; and besides its use in rails and fastenings (the latter including spikes, fish-plates, and bolts and nuts), and in the many thousand tons of car-wheels and axles annually required, there must be reckoned the almost unlimited number of castings daily required in the way of brake-shoes, pedestals, draw-heads, grate-bars, etc. The lumber and timber for buildings, bridges, platforms, and crossings, and the large quantity of glass which is necessary, are among other large items of expenditure.