422 Rural Architecture. 



sure due to the swelling of the wood and the rigidity of the 

 hoops will result in crushing the edges of the staves to- 

 gether so as to make a sufficiently tight joint to preserve 

 the silage. 



520. Lumber for Staves. The lumber selected for the 

 staves of this type of silo should be of the grade known com- 

 mercially as "tank stuff," and lumber freest from knots 

 and straightest grained is best. Wood is quite air-tight 

 under low pressures in directions across the grain but along 

 the grain the air passes more or less freely. The Washing- 

 ton cedar appears to be an excellent wood for this purpose, 

 as it shrinks much less than the pine after the silage is re- 

 moved and, for this reason, the building will be much more 

 stable when empty and less liable to burst the hoops when 

 filled. 



Where the silo is to be deeper than can readily be secured 

 with single lengths of lumber the staves may be spliced in 

 the manner represented at C, Fig. 208, where a saw-cut is 

 made in the ends of the two staves and a piece of galvanized 

 iron, a little wider than the stave is slipped into it. This 

 crushes into the wood on the sides and forms a water tight 

 joint 



521. Foundation of Stave Silo On account of the ten- 

 dency of the stave silo to work off from the wall when 

 empty a flat cement floor has been recommended, made of 

 sand and gravel or crushed rock, forming a bed of concrete 

 about 12 inches thick. This is perhaps as good as can be 

 done under the circumstances but it precludes the exten 

 sion of the silo into the ground. 



Tf the silo stands upon a stone wall, as represented in Fig. 

 208, it will be prudent to have a shoulder jutting into the 

 silo as much as 2 inches and a similar amount on the out- 

 side, to permit of some movement on the foundation. 



522. Hoops for Stave Silo. Five-eighths inch round iron 

 rods, in about 16-foot lengths, form the best hoops and thov 



