168 CONTROL OF EROSION .IN THE MOUNTAINS 



measures were begun in 1865, and on January 1, 1899, 1,547 acres had 

 been reclaimed at a total expense of $67,656.15, or about $42 per acre. 

 The species planted were chiefly Austrian pine and Scotch pine, but in- 

 cluded various broadleaf trees. The Scotch pine is to-day doing very 

 well. In another nearby project the cost was $40 per acre, divided as 

 follows : 



Cost of soil purchase $9. 10 



Corrective works (dams, drains, etc.) 11 . 60 



Plantations (grass, shrubs, trees) 19. 30 



Total .$40.00 



These costs would now be doubled or tripled, but today the difference 

 in the present rate of exchange and the normal must be deducted to get 

 the relative cost in dollars. 



A remarkable example of the control of a torrent which did a great 

 deal of damage from 1832 to 1847 is to be found at La Grollaz. The 

 correction work was started in 1880. To-day the torrent is a pretty 

 brook with waterfalls over artificially constructed cement dams protected 

 by an absolutely dense cover of alder, which holds the soil immediately 

 along the brook. Further up from the stream Scotch pine has been 

 planted, so that the result is a pretty New England trout stream bordered 

 by trees 50 feet in height. This illustrates the two great principles in the 

 control of erosion: first, to stop the earth from moving as a whole and, 

 second, to cover it with shrubs, nurse trees, and forest. 



TYPICAL REFORESTATION AREAS 



Regions. To give a picture of the conditions in the principal regions, 

 important reforestation areas (see Fig. 14, c) in the Alpes, sub-Alpes, Cen- 

 tral Plateau, Cevennes, and Pyrenees are described in considerable detail, 

 the material being furnished in the official report, " Restauration et Con- 

 servation des Terrains en Montagne." The routine and systematic 

 descriptions (given in the Appendix, p. 422) of the conditions following 

 erosion, and the tedious difficulty (see Fig. 14, c) of stopping the damage, 

 emphasize the dangers and costs of overgrazing and deforestation. 



