BUILDING THE SILO. 297 



much latitude in choice of material for staves, in 

 character of hoops and in furnishing of the roof. 



The Foundation. The character of the founda- 

 tion for the stave silo should be determined largely 

 by the character of the soil, and the size of the silo. 

 Stave silos have been placed on the surface of the 

 ground without any excavations whatever other than 

 that made by removing a few inches of the soft 

 surface soil. But in such instances they have stood 

 on a double thickness of bricks laid first in mortar 

 and then in cement. The mortar below should rest 

 on broken stones or gravel. This plan would seem 

 to answer v/here the soil is perfectly dry and the 

 silo is of moderate dimensions. In other instances 

 the wall is sunk several inches, that is to say, far 

 enough to go down to a firm subsoil. This plan 

 will probably suffice where the subsoil is dry and 

 winter frosts are not severe. In yet other instances 

 the wall goes down a little lower than the frost is 

 expected to penetrate. The wall should be sunk 

 thus far in all soils that are liable to be much dis- 

 turbed by the action of the frost. When it is neces- 

 sary to sink the wall several feet below the surface 

 of the ground, it will usually prove economical in 

 the end to excavate inside the wall to the same depth 

 to which the wall has been sunk. But when thus 

 excavated care must be taken to have the inner sur- 

 face of the wall made smooth with a lining of cement, 

 and to have the circle made by the inside of the 

 staves correspond exactly with the circle of the 

 stonework when lined as indicated. 



The stone foundation should not be less than 

 two feet broad and should come up several inches 



