The general location and importance of a transportation route depend first of all upon the activity and number of the people along its course, especially at the two ends. If the people are active they produce a relatively large surplus, and demand many goods which they do not themselves produce. Since they have to ship out their own surplus and bring in that of other regions to satisfy their demands, there must be much transportation of freight. Many passengers must also be moving back and forth to care for the equalization of surplus and demand which is thus going on. Hence the most important land route in the United States and perhaps in the world connects New York and Philadelphia. . These great cities not only exchange the products of their own hinterlands, but gather the surplus of vast areas both in the United States and abroad. Of the same nature although not quite so important are the routes (A) from Boston to New York, (B) Phila delphia to Baltimore and Washington, (C) New York via Buffalo and Cleveland or Detroit to Chicago, and (D) Philadelphia via Pitts burgh to Chicago or St. Louis. Other main routes run from Chicago and St. Louis westward to Seattle, San Francisco, and Los Angeles. In Europe one of the greatest routes is from London to Liverpool, while other great routes run from London to Paris, Paris to Berlin, to Vienna, and to Rome; from London to Berlin via Holland, and from London to Liverpool and Glasgow. Greater than any of these land routes, and greatest of all routes is the waterway that draws its traffic from Balti more, Philadelphia, New York, Boston, and smaller cities, crosses the North Atlantic, and divides again to Liverpool, Southampton, London, Cherbourg, Antwerp, Hamburg and other cities.
All these routes are alike in one great respect; the details of their location are determined by plains, valleys, mountains, lakes, rivers, ocean currents, harbors, winds, ice, or fog, but their general position depends on the fact that they connect centers of human activity. Fm example, the exact position of New York is determined by a fine harbor to which the Mohawk—Hudson Valley gives easy access from the interior. But suppose there were no such harbor and valley, the great Atlantic trade route would still terminate somewhere in that vicinity. It might enter America at Boston, New London, New Haven, or Philadelphia, but it would have to exist because the numerous demands of the active population of the northeastern United States would still continue even if there were no New York. Thus we conclude that great routes of transportation grow up because active regions need to be connected. When once the routes are established they are power ful factors in causing the cities which they connect to become larger.
In the world as a whole, the greatest routes connecting active centers generally run east and west. The transcontinental rail ways of the United States and Canada are of this kind; so too are the trans-Andes railway from Argentina to Chili, the great railway east and west along the southern side of Australia, and the trans Siberian road which connects the active Baltic portion of Russia with the active eastern Asiatic, region which centers in Japan. The greatest railways that have been planned to run north and south must traverse warm, inactive regions, but their aim is to connect active centers in the northern and southern hemispheres. The greatest of all such projects is the line that will presumably some day connect the northern United States with Chili and Argentina.. Another of the same
sort is the proposed Cape to Cairo Railway in Africa. On the sea likewise, the great routes generally run east and west to connect the great centers of trade, as appears from a comparison of ocean routeS, Fig. 31, with foreign commerce, Fig. 30, and civilization, Fig. 25.
How Physical_ Conditions Determine the Detailed Location of Trade Routes. (1) the general location of a transportation route has been determined by the centers of human activity, the details are determined by physical conditions. Other things being equal, the shortest route is chosen. Hence on the ocean, in the air, and on plains, the routes of transportation run almost straight except for the curve of the earth. Many railroads boast that they are " air lines," and on their time tables they often distort the maps in order that their lines may appear to be straight and short.
(2) is even more important than shortness. On the ocean or on lakes every route is level, while in the air no route can possibly be level. In this fact lies one of the greatest advantages of water communication over other forms, especially over communica tion in the air. In transportation by water nothing is lifted against the force of gravity; in transportation in the air everything must be lifted at least a few thousand feet and kept up. How much energy it takes to lift a body against gravity can be judged by trying to move a heavy automobile. On a perfectly smooth floor one man can start a vehicle weighing a ton or two, but he and several others cannot lift that same vehicle even an inch without a jack. So important is levelness that many long but level roads can compete with those that are much shorter but less level. For example, the " airline " between Boston and New York is shorter than any other but is little used because the hills not only cause it to go up and down but necessitate curves which limit speed and increase the cost of upkeep; the Delaware, Lackawanna, and Western route from New York to Buffalo (396 miles) is shorter I than the New York Central (439), but its hilliness much diminishes its business. So too, the Southern Pacific or " Sunset Route " from New York by sea to Galveston and then across the Rockies to Los Angeles and San Francisco, is much longer than the direct routes from New York via Colorado, but because it is perfectly level on the ocean and relatively level on the land it easily competes with the far shorter and more direct but highly mountainous routes farther north. Among these mountainous routes the Denver and Salt Lake Railroad follows the Old Mormon Trail, and is relatively direct, but the fact that it climbs to 13,000 feet had much to do with its going into the hands of a receiver in 1915. Hilliness has an indirect as well as a direct effect, for it causes the population to be sparse. Between New Haven and Boston the " air line " passes through no city larger than Willi mantic, while the " shore line " passes through New London, Provi dence,' and Pawtucket, and the Connecticut Valley line through Meriden, Hartford, Springfield, and Worcester. The largest cities on the short Delaware, Lackawanna, and Western Railroad are Scranton and Binghamton as contrasted with Albany, Utica, Syracuse, and Rochester on the New York Central.