The main effect of daily currents of travel is on the location of retail stores, increasing traffic being certain ultimately to change any street into a shopping street. As a corollary to this is the important fact that the relocation of the best residence districts is certain to change the axis of the principal travel within the city, which will draw the shops and values to new streets. Such changes of axis have taken place in New York from Pearl Street to Broadway, and from streets parallel to the river front to streets at right angles to it in St. Louis, St. Joseph, Minneapolis, and are now taking place in Toledo, Portland, Ore., and Cincinnati. As shops follow the shifting currents of travel, rentals move with them, the value of retail land depending on the number of people passing, qualified by their purchasing power, the causes which bring them past the. property and their method of locomotion. This dependence of retail business on daily traffic is due to the operation of the laws of chance, by which of a given number of passers-by a certain proportion will become customers.

The mention of traffic within a city suggests the double* function of a city street as contrasted with the single function of a country road. A country road is a means of communication only, while a city street also furnishes frontage for buildings. Ordinarily, city streets are first a means of communication and* later furnish frontage for buildings, but in waterfront cities this may be reversed. The principal business streets usually have some definite point of origin, such as a ferry or a railroad station within a city, or a country town or district outside of it, and long distance or through traffic is a prime essential for business streets, those which are cut off at one or both ends being almost useless for retail business, even though immediately contiguous to main arteries of traffic. Currents of traffic are not always straight, but may follow a street which has turns or angles, or a short street cut through a block between two main business streets, as with New Bond Street in London, and Union Street in Nashville. A serious detriment to values is caused by a break in the continuity of shops, whether due to a vacant lot, a church, a private residence, or an institution of any kind. A row of stores resembles a chain, the insertion of a vacancy or of any different utilization breaking its cohesion.

Besides the main currents of travel, the little feeding streams are closely watched, such shops as hatters, tailors, lunch rooms, men's furnishing goods, etc., locating in the men's district near the office buildings. The grade of shops on the streets leading from the office sections conforms to the character of the passers-by, high-class shops being where employers pass, and cheaper shops where clerks go, while push-carts and hawkers catch the office boy trade.

A noteworthy qualification in the location of retail shops is that the larger and more expensive the articles to be purchased the further people will go in search of them. Large and well managed shops will attract purchasers wherever located, but even such shops are. extremely sensitive to the merits of different locations and pay high rents to be exactly where they can obtain the largest number of customers. In all cities there are constant changes in the population, and all shops to be most successful must keep themselves before the public by means of prominent locations.

The most striking feature of the daily travel within a city is its fluidity, or the. closeness within which it seeks its own level. Obstructions check it and turn it aside as they would a stream of water. In flowing down a street it backs up each cross street, carrying stores to a distance proportionate to the strength of the current; and where two currents meet the pressure at the intersection intensifies the back currents. The stronger the current the further it spreads back or the greater the depth of shops, in some cases running through the block, as on 23d Street, New York, where the shops extend to 22d Street on one side and 24th Street on the other. Similarly, the stronger the current of traffic the higher it is heaped up, or the taller the buildings to accommodate it. The current of travel blocked by Washington Square, New York, flowed up Broadway and 6th Avenue and meeting at 23d Street, a back current of business building has flowed down 5th Avenue, in the same way that a stream meeting a rock divides, the pressure of water causing a current to flow back to the rock.