PHYSICAL, ECONOMIC, AND SOCIAL 383 



Frost. — Around the forest, but not in it, one finds the white frosts which are so 

 common in dry dimates. The upper story protects the lower vegetation hke a tender 

 blanket. It replaces, after a fashion, artificial shelter. 



"Wind. — Without the trees in numberless countries, the violence of the wind lays 

 low the plants or dries them up. . . . The smallest shrub or the simple hedge of 

 cypress of the Provence exercises a beneficial protective cover. In Russia, when the 

 June vegetation of the steppes is in full bloom, the squares enclosed with planted hedges 

 remain green, and furnish half again as much revenue. In Algeria, they say that nothing 

 can resist the sirocco. Nevertheless, it has been conquered by the trees. Look at 

 the delicate plants in the experimental gardens at Algiers and the rich plantations of 

 the Mitidja. . . . 



Springs, Avalanches. — All the world to-day bears witness to the benefit of the 

 vegetable cover for the maintenance and conservation of springs (see Appendix, p. 

 361). This is also true of the value of forests in protecting against avalanches. 



Floods. — The forest is the sovereign regulator of waterflow. On the denuded slope, 

 the rain rushes along carrying the material eroded from the loose soil. This mass, 

 increased by the mixture of debris, and with its increasing speed, communicates a 

 tremendous live force to these thousands of little streams. It becomes a furious tor- 

 rent which carries off the slopes, bears rocks along and even fields and houses. Gravel 

 fills the bed of the rivers and hinders shipping. It covers the plain with blocks of stone 

 and sterile sand. What would happen, on the other hand, with a wooded slope? A 

 large proportion of the rain will have been stopped by the foliage and branches to be 

 given back to the atmosphere. The remainder, broken up by the foHage, strikes the 

 soil as if it had passed through a sieve. The layer of dead leaves and humus which 

 carpets the forest floor is a soft sponge with an extraordinary capacity for absorption. 

 It absorbs five, six, and even nine times its liquid weight before saturation, when it 

 lets the water seep, drop by drop, to the surface and to the interior of the soil to feed 

 subterranean streams which result in springs. The small surplus water, which is not 

 retained, encounters in its flow innumerable obstacles, trunks, roots, moss, herbaceous 

 flora, dead branches, dead leaves, and the inextricable lacework of roots. The flow is 

 divided slowly up and does not erode the soil. It arrives at the foot of the slope slowly 

 and in small quantities. . . . Against the heat of the sun and the drying winds 

 of the south the branches serve as a screen. In the spring they diminish the damaging 

 effect of warm rains on the snow and prevent too rapid melting. The regularity of 

 the run-off is determined by the state and extent of the forests which cover the basin. 

 Numerous experiments in valleys, some forested and others bare, have proved this. 

 These comparisons have given rise to the adage: "He who wishes to master the waters, 

 must first master the forests." Thus to the trees crowning the mountains the soil is 

 held in place. The slopes are maintained and erosion ceases. Its action can thus be 

 summarized : 



"The presence of forest stops the formation of torrents. Its development extin- 

 guishes it. Its destruction delivers the soil as a prey to erosion. All the fundamental 

 laws recognize the absolute necessity of reforestation. In the denuded countries, what 

 ravages! The torrents attack the mountainsides like a 'pieuvre,' eat them out, dis- 

 integrate and carry them piecemeal to the plain. High up the rock is bared, lower 

 down they cause the fields to become barren and covered with debris. The roads 

 are interrupted. The railway lines cut and the bridges demolished. One sees the 

 opening up of abysses, the cut of railroad lines, and the engulfment of entire villages. 

 Each year, in France, the floods cause an average damage of $5,790,000. With the 

 expense, which has been caused by such floods during the 19th century, all Europe could 

 have been reforested. These catastrophes have been the result of excessive deforesta- 



