249 



to start, which testimony, however, must be verified by a careful study 

 of the natural couditioiis of the locality. Usually the place of begin- 

 niug lies higher up than observed. If the start lies ou extensive, steep, 

 rocivy faces, there is no use in trying to secure it ; if there are only In- 

 terrupted walls and rock portions, or if a ravine form the starting place, 

 securing is possible, and the question then simply is, whether the cost 

 of doing so is in proportion to the benefit to be derived. 



The works consist of walls or woodwork, or a combination of both. 

 Ditches are not without influence, but are by no means as effective as 

 wall and woodwork, and present, besides, several objections j they are 

 collectors of water, which is liable to carry away the earth work; they 

 are soon filled up or trodden down ; similar objections exist to terraces. 



The choice of stone or wood for safety works depends mainly on the 

 costliness of either. Above the timber line stone would of course be 

 preferable, below the line it is employed oul^^ where reforestation, and, 

 therefore, temporary constructions are not possible. 



Wood structures consist of rows of pile work, for which of course the 

 most durable wood obtainable in the region is used. Split wood is 

 better than round, which latter does not hold the snow as well. The 

 piles are usually made 4| to 5 feet long, and have a diameter of 5 to 6 

 inches. Preserving processes, charring, etc., are unnecessary in the 

 altitudes where this work is to stand. The posts are pointed at one 

 end, and driven with a wooden wedge, so as not to split them, if pos- 

 sible, 2J feet into the ground, perpendicularly to the horizontal plane, 

 and secured with stones. They should not be above ground more than 

 3 feet, and on thin soil not as much. 



The intervals between the piles should be 2 feet. It is not necessary 

 to connect them by wicker work, as the snow does not slide through 

 the piles ; but where the ground is thin, or very dry, or very steep, or 

 otherwise lacking in hold, such wicker work may be made of branches 

 to connect, and thus to strengthen the piles. The two end piles must 

 be especially secured. The length of the rows of piles and their dis- 

 tance from each other depend upon the configuration and the angles of 

 inclination of the ground. 



The choice of the place where the row of piles is to be put is of im- 

 portance. The work is begun at the top or starting place of the av^a- 

 lanche and progresses downwards. The piles must be driven in the 

 horizontal line, so that the pressure of the snow will be evenly distrib- 

 uted over the whole line. They are also to be placed where a change 

 of fall (angle of inclination) from a less steep into a steeper incline oc- 

 curs. If no natural terraces are found, such may be made by cutting 

 into the ground above the piles, making a terrace of 2 feet in the side 

 of the mountain. The ground thus removed is placed on the lower side 

 of the piles and covered with turf. 



Where piles can not be driven " snow-bridges " are constructed 

 Where narrow rills or runs are to be protected a tree is thrown across 



