CONTINENTAL NOTES — FRANCE. 7 I 



Ebermayer, moss retains 70 to 80 %. After Volny, turf retains 

 half of the water a bare soil would allow to sink in. After 

 Schloesing, a forest soil retains 42 %, or 10 % more than a limey 

 clay soil. According to the German Research Stations 44 out 

 of 100 millimetres of water falling on a forest soil will penetrate 

 the upper layers, whereas with uncovered soil the figure would 

 be 31. M. Viney therefore thinks that it would be reasonable 

 to assume that an ordinary soil, 8 to 12 inches deep, covered 

 by old coppice growth, would retain 2 inches more rain than 

 waste land or bad pasture, which is the same as 500 cubic 

 metres to the hectare (7149 cubic feet to the acre). The retain- 

 ing capacity and the rate of absorption must go together, other- 

 wise the water coming from a violent and continuous rain wili 

 pass off at once. Thus, a free gravel soil above rock will 

 rapidly pass off the water along the top of the rock, and 

 similarly a close-grained clay with a retaining capacity of 70 7o 

 will, after the surface is wetted, pass the water off the surface as 

 does an impenetrable rock. The two qualities must go together 

 if there is to be a properly regulated flow of water. And these 

 two qualities are in fact found in the highest degree in a forest 

 soil, with its sponge of humus, moss, etc., and its network of 

 roots, which take the water down into the deep layers. Slopes 

 of loose, unprotected soil are cut up by rain, the damage 

 continually increasing, and spates and inundations result. 

 Everything points to the necessity of checking the flow. 

 Nothing does this like forest, which first prevents the dash of 

 the rain on the surface, and then checks the flow by its spongy 

 nature, while the roots hold the soil together. Still, it may be 

 noted, even the best holding soil will sometimes reach its limit 

 of saturation, and then the excess runs off the surface, so that 

 even a forest soil cannot altogether stop floods. 



Though the action of forests on floods is incontestable, and 

 very marked, and much more so where the slopes are steep than 

 in low country, yet, as said at the beginning, it is not fair to 

 expect impossibilities from afforestation. Thus, whereas it was 

 calculated that from the rainfall in November and December 

 1909 an excess of 4I inches of water ran into the Seine (not 

 merely fell on the area), had as much as 400,000 hectares 

 (988,000 acres) out of the 12,000,000 acres of the basin above 

 Paris been afforested, in addition to the existing wooded area, 

 this would only have absorbed 7064 million cubic feet (on the 



