LINE CONSTRUCTION. 
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of stonework, or stakes driven into the ground. The direction 
of the stays must be opposite to that of the resultant of the 
forces that act on the post. The depth to which the posts are 
sunk depends on the nature of the soil and the resistance to be 
overcome ; but in land of fair solidity, such as clay or sandy 
clay, this depth is generally from 5 feet for posts 20 to 30 feet 
high, feet for posts 32 to 46 feet high, and 10 feet for posts 
65 feet high. In soils formed of quartose, calcareous, or 
schistose rocks, the holes must be made by blasting or by 
jumping-tools. In such cases the depth is seldom more than 
2 feet. The distance from post to post is commonly 100 yards 
in a straight line and 50 yards in curves. 
Posts bearing stretching apparatus are placed every 1,000 
yards. If two lines follow the same road, the most important 
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