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Page:Popular Science Monthly Volume 19.djvu/853

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FOREST-CULTURE IN ALPINE RAVINES.

then sowing the seeds of grasses in the intervals. Concurrently with these preliminary operations, the only object of which is to prepare the soil for the reception of the forest-growth to be planted later, the torrent itself is attacked with works intended to impede its course, hold back the drift-matter, and prevent further undermining of the banks. For this purpose wattles and bars are inserted along the stream and its smallest ramifications, beginning generally at the upper parts, where the water, not having acquired its full force, can be more easily stopped, and the suspended matter may be more easily retained. Green branches of willow and hazel are woven around stakes in the ravine, take root in the soil, and become a living obstacle which perpetuates itself. If the wattles are close enough together, they will transform the ravine into a kind of staircase, by the agency of which the violence of the water is allayed at each step, its force is lessened so that it does not wear upon the soil, and it is made to run almost clear.

More energetic measures are required lower down, where the torrent exercises a more destructive action. Here dams of masonry are inserted in the banks, provided with an arched channel in the lower part to permit the outflow of water at moderate stages of the stream; they serve to hold back the stones that are worked out from the mountain, to promote the growth of alluvions, to break the fall of the torrent and diminish its violence by enlarging its bed. Some of these dams are real works of constructive art, and have cost as much as eight or ten thousand dollars.

The real replanting of the woods is done after the ground has become settled and the torrent has been subdued. Nurseries of young trees suitable for the purpose are previously established near the locality of the works, which are drawn upon as the plants are needed. The species vary according to the nature of the situation and the soil. Generally pines and firs of different kinds are best adapted to the higher situations, deciduous trees to the lower ones. Use has also been made of several species of shrubs and bushes, which with their branching roots are wonderfully fitted to fix the earth, and by reason of their rapid growth quickly furnish a shade to the bare surface. The planting is begun at the top of the elevation and is conducted downward, in such a manner as to leave no places vacant. The young trees, protected against the sun by the grasses which were previously sown and by the willow-cuttings which have already taken root, soon begin to grow with vigor. An effort was made, in accordance with the law of 1864, to substitute regrassing for replanting with wood in the interior of the perimeters; but it did not answer the purpose of consolidating the soil, and was abandoned. Sometimes the communes have shown themselves hostile to the execution of these works on account of the interdiction of pasturage. Such was the case in the communes of Orres and Saint-Sauveur, whose inhabitants drove away the workmen in 1864. The work was resumed three