Mechanical Break—It is quite obvious that a break of the first sort is of much less importance than one of the second. Even a mechanical break may, however, bring together a good many persons and lead to the development of considerable structures. At these locations there must be loading, unloading and intermediate carriage of some sort. Buildings are required for storage and persons to care for them and for the goods they contain. Some sort of provision must be there for the instruments of transportation—ships, camels, railroad cars, or whatever they may be. All these facilities were required during the process of loading and unloading. Provision also had to be made for the persons that accompanied them. Around this group of specialized personnel a corresponding agricultural, artisanal and shop-keeping population had to be present.

According to Cooley a commercial break arises almost always at or near the physical interruption and thereby increases its importance. Where a break of this sort exists on an important line of transportation—though it might be in the midst of a desert—a commercial city develops. The reason is not difficult to imagine. At a commercial break there necessarily arise, beside the machinery of transfer and storage, the highly organized personnel and appliance of economic exchange. Over a period of time there arises a class of merchants and money-changers, who require buildings with more elaborate facilities for carrying on with their business. Their splendid lifestyle draws together a relatively large and heterogeneous subsidiary population. The nucleus thus formed, it tends to become the seat of political power, and of the central institutions of different social organization. Very often the commercial capital usually becomes the political capital and is commonly the seat of the chief temples and of the culture and art.