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.