Now, a special and most suggestive feature of transportation by steam, electricity or other kinds of mechanical force is that its capacity is not only unmeasured and unknown, but will doubtless prove to be virtually inexhaustible. That is to say, no certain limits can be assigned to the operation or effect of these new agencies as compared with those which have been supplanted. Therefore, speed may reach many times the rate now attained, the size of vehicles may be greatly increased and the cost of carriage for the longest distances reduced to an astonishing minimum; so that, as progress goes on in developing the means and methods of distribution, the habits and needs of men will be more and more modified, with consequences to social order and the general conditions of life which may be far greater than have yet been imagined. Among the results already realized, which directly forecast what will further happen, some of the more obvious may be briefly mentioned. For well understood reasons the speed and capacity of water craft are much superior to those of vehicles drawn by animals, while the cheapness of the former gives them a great advantage over the latter. While the old conditions prevailed, the waterways were mainly relied upon for the conveyance of bulky products. Commercial movements on land were, of course, considerable, but the transfer of heavy goods, such as enter most largely into ordinary consumption, was principally effected by sailing vessels. Therefore, the fertile lands along the river-banks and the indented shores of the sea were the first to be occupied for agricultural pursuits, the exchange of produce for merchandise being accomplished by water carriage. The great cities founded prior to our time were for the most part located upon or near navigable streams while the masses of population outside the towns dwelt within easy reach of these natural channels. But the building of railroads has often deflected and sometimes wholly altered the routes of distribution. In our own country, for example, notwithstanding it is penetrated by numerous rivers which flow, generally speaking, from north to south, the great volume of traffic is carried by railways running east and west across valleys and mountains. Even where the rail lines are parallel with river courses they absorb the greater share of freight and passenger movement. In short, the routes of land transportation in all the principal countries of the world have been largely recast in the last fifty years by the changes from river to rail conveyance.