112 CHYMISTRY APPLIED TO AGRICULTURE. 



firmly iu a sandy and easily disturbed soil. The winds 

 are generally very violent in those valleys through which 

 large rivers flow ; and these, by the violent motion which 

 they give to the branches, twisting them in every direc- 

 tion, loosen the roots ; and the earth being continually dis- 

 turbed, the water penetrates in, and softens it, so that when 

 an overflow of the river happens, the breaches thus made in 

 the soil lessen its powers of resistance to the flood. 



If we observe carefully the action of currents upon tlie 

 great trees surrounding lands situated upon the banks of a 

 stream or river, or upon an island lying in the course of 

 one, we shall be convinced, that, so far from preserving, they 

 facilitate the destruction of property ; for as the trunks op- 

 pose an invincible resistance to the force of the current, it is 

 divided, and, encircling them, it meets again, having former! 

 a complete trench in the soil. Thus, though large trees 

 may be useful for turning aside masses of ice, and prevent- 

 ing the land from being much injured by them; yet in- 

 stead of preserving it from the ravages of a rapid current, 

 they become powerful auxiliaries to its destructive action. 



Flexible shrubs are undoubtedly preferable to large trees ; 

 their roots bind the soil ; their branches lie upon the sur- 

 face of the earth, and preserve it from injury during floods ; 

 but these shrubs do not present any resistance to the ice 

 when the rivers are breaking up ; they cannot turn aside 

 the masses of it, and force them to remain in the bed of 

 the river, that they may not furrow the meadow or field. 

 It is necessary then to unite the resistance offered by trees 

 ■^ with that of flexible shrubs : in order to do this, it is neces- 

 sary to plant willows or poplars on the extremity of the 

 banks, at the distance of seven or eight feet apart ; the 

 heads of these may be cut off" some feet above the height 

 to which the highest floods ever reach ; the water willows 

 or osiers may be planted all along upon the shelf or slope 

 of the land, and from twenty-five to thirty feet inward. In 

 a few years there will be nothing to fear from floods or ice 

 upon land defended in this way ; and a considerable reve- 

 nue will arise from the pruning of the trees, and the clip- 

 pings of the osiers. 



After having placed the land out of danger from inunda- 

 tions, the neighbourhood of a river opens sources of profit 

 that are very simple, and may be taken advantage of at a 

 slight expense. I have heretofore remarked, that the mud 

 of rivers is of great use as an amender of soils, and that 



