EVILS FOLLOWING DESTRUCTION OP POEESTS. 79 



comprises 50 hectares of cultivated lands, that of the other 

 250 hectares of woodlands. The first receives, and allows 

 to flow away, the waters of the greater part of a storm in 

 a few hours at most, causing thereby considerable damage ; 

 the second, which had received a greater quantity of rain, 

 stores it — keeps it for two days — evidently retaining a 

 portion of it, and takes three or four days to yield up the 

 surplus, which it does in the form of a limpid and inoffen- 

 sive stream.' 



M. Jules Clav^, writing on the effects of forests in 

 increasing humidity of soil, says : — ' When Napoleon was 

 taken to Saint Helena,' writes M. Blanqui, ' the English felt 

 the necessity of occupying Acension Island, which was 

 then only a barren rock, scarcely covered with a few 

 cryptogamic plants, and there they stationed a company of 

 a hundred men. At the end of ten years this little garri- 

 son had been enabled, by dint of perseverance and planta- 

 tions, to create a soil on the island, and from this to draw 

 some water. It was abundantly planted with vegetables. 

 Such was the result of plantation upon a rock in mid- 

 ocean ! 



' But why should we seek so far away for the proofs of 

 phenomena that are renewed daily under our eyes, and of 

 which any Parisian may convince himself without ventur- 

 ing beyond the Bois de Boulogne or the forest of Meudon ? 

 Let him walk out, after some days of rain, along the 

 Chevreuse road, bordered on the right by the forest of 

 Meudon and on the left by cultivated fields. The amount 

 of rain that has fallen is the same on both sides, and yet 

 the ditches by the roadside along the edge of the forest 

 will be still filled with water, proving the infiltration going 

 on from the wooded soil, while already for some time those 

 on the other side, adjoining the cleared fields will have 

 been dry, after having served their purpose by a sudden 

 flow. "The ditch on the left will have emptied itself in a 

 few hours of all the water, which the one on the right will 

 take some days to convey to the bottom of the valley.' 



