Of roads and tracks throughout this vast area there were but few, and these were mostly either indifferent or bad, even if they did not become positively execrable in wet weather or after a considerable force of troops had passed along them. In the low-lying districts, especially, the alluvial undrained soil was speedily converted by the winter floods into swamps and lakes. Further difficulties in the movement of troops were offered by pathless forests as large as an English county; and still others by the broad rivers or the mountain ranges it might be necessary to cross. Apart from the deficient and defective roads and tracks, the transport facilities available for the combatants were those afforded by coastal services, navigable rivers, canals and railways. Of these it was the railways that played the most important rôle. The American railway lines of those days had, generally speaking, been constructed as cheaply as possible by the private enterprise which--though with liberal grants of land and other advantages--alone undertook their provision, the main idea being to supply a railway of some sort to satisfy immediate wants and to improve it later on, when population and traffic increased and more funds were available. The lines themselves were mostly single track; the ballasting was too often imperfect; iron rails of inadequate weight soon wore down and got out of shape; sleepers (otherwise "ties"), which consisted of logs of wood brought straight from the forests, speedily became rotten, especially in low-lying districts; while, in the early 'Sixties lumber, used either in the rough or smoothed on two sides, was still the customary material for the building of bridges and viaducts carrying the railways across narrow streams, broad rivers or widespread valleys. All the same, these railways, while awaiting their later betterment, extended for long distances, served as a connecting link of inestimable advantage between the various centres of population and production, and offered in many instances the only practicable means by which troops and supplies could be moved. They fulfilled, in fact, purposes of such vital importance from a strategical point of view that many battles were fought primarily for the control of particular railways, for the safeguarding of lines of communication, or for the possession, more especially, of important junctions, some of which themselves became the base for more or less distant operations.