Does not this constitute local discrimination against the middle western cities? This was one of the main contentions in the St. Louis Business Mens' League case. Being one thousand miles nearer San Francisco, it demanded recognition of that fact in its tariffs. The difficulty is accentuated when both eastern and western point rates are considered together. St. Louis enjoys no lower rate than New York, although one thousand miles further east; and inland points in the Rocky mountain area may be one thousand miles further east than San Francisco and yet pay a higher rate. Thus it is possible to lop off one thousand miles at each end of the line without affording any recognition of it in the tariffs. The situation is too involved to discuss in detail in this place; but one finds it difficult to avoid the conclusion that the whole system will demand revision before long. Geographical conditions are immutable. Trade conditions are not. Perhaps it was inevitable that the former should by force of circumstances have been somewhat overlooked during a period of rapid growth. But, as commercial affairs approach a condition of stability and permanence, the matter will call for most careful examination. [Illustration] Constant rates applied over long distances on the same line almost inevitably tend to pass over into a system of equality of rates over _different lines_.[230] The necessity was evident enough in the Milk Rate case. This phase of the matter may theoretically best be discussed by reference to the following diagram. Suppose A, B, C, and D to represent any four inland "common points." It remains to show how it comes about that they all finally enjoy equal rates to all four seaports, regardless of location. Each appears to be naturally tributary to some one of the seaports by a dominant or short-line route. In each instance this route properly rules the rate. Moreover, the four seaports may be considered for traffic purposes as equally and interchangeably distant from one another without regard to location. This follows from the fact that, except in extreme instances, rates by water do not vary according to distance, so small is the cost of mere propulsion by comparison with the terminal costs. In other words, the rate is the same from Wilmington to Brunswick or Savannah as to its next neighbor Charleston. From this it follows, further, that Wilmington, Savannah, and Brunswick can all reach B--the point to which Charleston is nearest--on even terms. They may each have a direct line to B; but, as compared with a possible combined low water rate to Charleston and a low direct rail rate inland to B, the Charleston route may be at least able to hold its own. All three outside competitors, then, are on even terms with one another in respect of access to B. But how does Charleston stand towards B as against the field? We have already concluded that a roundabout route must be allowed to meet, though not to undercut, the ruling rate.