Two general theories governing the rates chargeable by railways are entertained, known respectively as cost of service and value of service. According to the first, the proper rate for transportation should be based upon the cost for carriage of the persons or goods, with an allowance for a reasonable profit over and above the expenses of operation involved. This line of argument is commonly advanced by representatives of shippers and the public, who reason by analogy from other lines of business. In several European countries when railways were first built, and afterward, especially in Germany in 1867, attempts were made to apply this principle widely in the construction of tariffs. Practical railway men, on the other hand, usually adhere to the second principle of value of service. This argument maintains that, while theoretically cost of service should determine minimum rates, owing to the nature of commercial competition, as a matter of fact rates must be based upon the principle of charging what the traffic will bear. This is accomplished by proportioning the rate to the commercial value of the service. Practically the rate is found by charging as much as the traffic will stand without evidence of discouragement. Thus if the price per bushel of wheat in New York is twenty-five cents higher than in Chicago, it would obviously be absurd to charge a rate which would absorb all of that increment of place value due to transportation. Enough margin must be left to the shipper who buys wheat in Chicago and sells it in New York, to permit a reasonable profit on the transaction, after payment of the freight rate.