1526. Progress and impetuosity are the two leading ideas which belong to running waters. The first expression may be heightened by counteracting any tendency to expansion; by removing some of the circuitous and oblong projections of earth or stone in the banks; and sometimes by deepening the bed, or by substituting a more direct line for a circuitous course. The idea of impetuosity is indicated by its effects, in reverberating against high banks, or common banks, on which trees are situated, and may be increased by augmenting the cause or the effect, either by digging and undermining the trees, cutting down the high banks on which the water acts, or placing very slight piers as jetties on the opposite shore. Picturesque additions to the marginal accompaniments both of rivers and rills will readily suggest themselves. Cascades and waterfalls may sometimes be created; and the occasional expansion of natural brooks into pools affords a fine hint for imitation, when this form of water comes within a scene of improvement. One of the greatest improvements that can be made in many places laid out in Brown's time, and subsequently, consists in widening in some places, and varying the margin in others, of those tame serpentining canals, then so much in fashion. By this means, and by adding islands and trees, they may often, without deranging the place as to other details, be rendered highly beautiful at a moderate expense (fig. 250.).