FARM STRUCTURES 



409 



one inch wide with loads uniformly distributed. If the load 

 be concentrated at the center, divide by two. 



For oak or Northern yellow pine, the tabular values may 

 be multiplied by 1^; f r Georgia yellow pine, by 1%. 



For a discussion of the materials used in the construction 

 of farm machinery, see Chapter XXXI. 



Safe Load in Pounds for White Pine or Spruce Posts.* 



Oak and Norway pine posts are about one-fifth stronger, 

 and Texas pine and white oak are one-third stronger. 



Stone. Limestone and sandstone are the kinds of stone 

 generally used for building purposes. Granite is used to a 

 limited extent. Limestone is the most common stone used, 

 and when dense and compact is very durable. It often con- 

 tains certain substances which cause the stone to become 

 badly stained after being in use for a time. Limestone has 

 an average compressive strength of about 15,000 pounds per 

 square inch and weighs from 155 to 160 pounds per cubic foot. 



*Kidder's Pocket Book. 



