Sometimes they occupy the approaches to tablelands, the narrowest points of gorges, or the fords of rivers; sometimes almost inaccessible mountain tops or important points on ridges; and it may be noticed that, where two important nuraghi are not visible from one another, a small one is interpolated, showing that there was a system of signalling from one to another.
Some interesting manoeuvres now took place, Wellington moving parallel and close to Marmont, but more to the north, making for the fords of Aldea Lengua and Santa Marta on the Tormes nearer to Salamanca, and being under the belief that the Spaniards held the castle and ford at Alba on that river.
Kruger then closed the drifts (or fords) on the river by which the wagons crossed.
Crossing the Forth unopposed at the Fords of Frew and passing through Stirling and Linlithgow, he arrived within a few miles of the astonished metropolis, and on the 16th of September a body of his skirmishers defeated the dragoons of Colonel Gardiner in what was known as the "Canter of Coltbrig."
It divides its waters, splitting into many channels, leaving broad central islands; and as the width increases, and the depth during dry seasons diminishes, opportunities for fords become comparatively frequent.