250 
and secured at its ends against other trees, or by posts, or placed upon 
trestles, if necessary, supported in the middle by posts. Over this tree 
are placed sticks, with a slight inclination to the mountain side, some- 
what in the shape of a corduroy bridge, and fastened with wooden 
nails to the tree and secured by stones on the ground, if possible. 
Tie retaining- works of stone are the strongest, most lasting, and are 
possible everywhere, but also the most expensive. For a foundation a 
space of about 3 feetis leveled, with a slight inclination into the mount- 
ain side, as if cutting out a road; the base must be natural, not made, 
soil. The proper making of this foundation-base is of the highest im- 
portancve. The height of the wall must be 3 feet above the ground on 
the upper side; the steeper the ground, therefore, the higher necessa- 
rily becomes the wall work. Simple dry walls are all that is needed, 
which, in addition to being cheaper, permit rain and snow water to seep 
through. 
Especially the ends of the wall must be well secured, and the use of 
cement in this part of the wallis recommended. ‘The roof is made of 
large slabs or, in their absence, of sods. 
The length of walls, as of pile rows, depends on the configuration of 
the soil. The distance of the walls from each other may be greater than 
with wood-work. 
There have also been used iron rods let into the rock and covered 
with wood-work. 
The choice of work and the adaptation to the configuration is of 
greatest importance. 
If the slope presents an even surface, like a roof, the pile rows and 
walls are placed at intervals, so that the next series covers the even 
spaces of the one before. 
In ravines, the work is to be placed where the slope changes to the | 
steeper wall. Large bowlders or rocks rising above the surface are often §& 
the incipient cause of slides. The safety-work is to be placed at their 
foot, so, however, that the snow sliding from such elevations should 
not fall upon the wall, but in front of it, to be there retained. 
Springs and collections of seepage water must be taken care of and 
properly conducted. | 
A yearly inspection and repairs are, of course, necessary. 
After the starting-point of avalanches has been thus secured reforest- 
ation is at once begun, with such species as belong to the locality. | 
The planting is done with seedlings, at a distance of 40 inches, as a §, 
rule. This reforestation of the tracks of avalanches, especially in steep | 
situations, including after-planting, is very expensive,and amounts te 7. 
$25 to $406 per acre in Switzerland. | 
In conclusion, it may be stated that the Swiss Government bears 40 | 
per cent.—in extraordinary cases 59 per cent.—of the cost of building 
retaining-works. In reforestation in existing protective forests, 20 to 
50 per cent., and in planting new forests, 30 to 70 per cent. of the cost is | 
borne by the Government, the communities being liable for the balance. 

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