Of the domestic animals which have assisted man in the work of transport there can be no doubt that the horse is by far the most valuable. It is the strongest, the swiftest, and the best fitted for man’s purposes. The camel, of which so much has been written, is in point of fact a poor substitute for the more valuable animal, rendered necessary by desert conditions. Among the other animals which have played their part as beasts of burden or of traction are many kinds of ox, including the yak of Tibet; the llama of South America; the elephant; the reindeer; the dog; and the animals which rank as horses to the zoologist though not to the owner—that is the ass and the mule.

Just as the use of beasts of burden is an enormous improvement upon human porters, and that of wheeled vehicles upon beasts of burden, so is the use of steam an enormous improvement upon wheeled vehicles drawn by animals. Railways have practically revolutionised the problem of land transport, though their cost, especially in countries of marked relief, is a great drawback to their universal use. The last few years have seen in the development of motor-driven vehicles a new change, which has given back to the roads their old importance, and which will probably in the future greatly aid the development of new countries, and take from the railways some of their importance. It is too soon yet to say whether the last development of means of transport, the aeroplane, is destined to affect greatly man’s movements and methods of exchanging commodities.

In connection with means of communication a few words must be said about towns and their position, a subject in which the “new geography” has been greatly interested. In this chapter we have assumed that the progress of civilisation means, and has always meant, an increasing desire on the part of man for freedom of movement, and an increasing number of wants, which have led in their turn to an increasing desire for the exchange of commodities. The desire to possess efficient tools and weapons first attracted him, as we have seen, to the localities where useful minerals occurred. The new powers so obtained increased his desires, and also his mobility, and tended to make him cluster round the spots where his new desires could best be gratified. At a very early stage the desire to exchange commodities must have led to the founding of towns, whose number and size have increased with the passage of time.

Of the various causes which have led to the founding of towns at certain spots, some are obvious. That which has always attracted most attention perhaps is the fortress town, placed on some rocky peak, and commanding a well-marked route. But though such towns are imposing, and seem easily explained, it is obvious that at no stage of his history has warfare been man’s chronic state. Even at the worst period, if there had been no busy group of traders at the foot of the fortress-crowned rock, its significance could only have been trifling, and almost all fortress towns show, in the proximity of another agglomeration more suited to normal human activities, that the fortress itself was always rather spectacular than significant. Edinburgh, with the old city sloping down to the plain from the great rock, Carcassonne with the real city some distance from the theatrical erection on the hill, are two examples which illustrate this fact.

One or two of the chief economic causes of towns may be noted. They tend to occur where there is a “break of bulk” in goods being carried from one region to another. Such break of bulk now takes place at the great ports where the liners unload, but in the old days the small ships came up the rivers with the tide, and towns tended to occur at the tidal limit, as, e. g. at Newcastle-on-Tyne. Towns tend also to occur near natural obstacles to easy transport. Thus we have in England a great number of “bridge towns,” placed at the point where an important river was easily bridged or forded, and thus where co-operative effort was necessary to smooth over an obstacle. Towns tend to occur also where two regions of different natural products meet, for here the inhabitants of the two regions meet for the purpose of exchange of goods. Milan, at the foot of the Alps and yet in the plain, is a good example, for the products of the plains are not those of the mountains.

Many cities owe their origin and their fame to some event, often some religious association which draws great numbers of pilgrims and others. It is often doubtful, however, to what extent the supposed cause is the real cause of the city’s importance. Not every saint founds a city, not every holy city keeps its fame, and in the struggle for existence those cities will persist whose natural advantages are greatest.

Another very important cause of cities is a junction of routes, for this means that many different types of merchandise will pass this way, and will give abundant raw material for many minor industries. London is a good example of a town upon which many routes converge, these being both land routes and water routes.

Even these few examples may serve to suggest the point of view from which the modern geographer regards towns, and to illustrate the fact that in this as in other branches of his subject his interest is in the study of causes and of interrelations.