THIRTY-FIFTH ANNUAL CONVENTION. 259 



surface and the door placed over it and when the pressure of 

 the silage comes against the door an air-tight joint is obtained. 

 Tar paper is successfully used by some silo owners either in 

 strips to cover the cracks around the doors or in widths suffi- 

 cient to cover the entire door and lap a few inches on the silo 

 walls. 



In addition to being air-tight, the silo wall must prevent the 

 loss of moisture from the silage. Porous walls, which sap the 

 juices from the silage and transfer the moisture to the outside 

 of the wall where it will be evaporated, cause the silage to 

 become dry and moldy for a considerable distance inward. If 

 porous material is used for the wall, some provision must be 

 made for sealing it and making it water tight. In masonry 

 silos a plaster coat of rich mortar may be used successfully. 

 A cement wash will often be just as satisfactory, and a coat 

 of coal tar has been used successfully in the same way. Con- 

 crete silos have been known to preserve the silage more per- 

 fectly after two or three fillings, a fact which may be accounted 

 for by a gradual sealing of the walls by material from the 

 silage. 



Not only should the walls be tight and rigid, but they should 

 also be perfectly smooth on the inside to permit the silage 

 to settle without forming air pockets, which cause a certain 

 amount of the adjoining silage to rot. The foundation 

 wall, and in fact the walls of- the entire silo, should be as 

 smooth as possible. If due care is used in tramping the silage 

 during the filling, doors which extend into the silo are not a 

 serious objection, though perfectly flush doors are certainly an 

 advantage. A vertical wall is the only satisfactory wall to use, 

 as a wall inclined outward will support the silage to a certain 

 extent and prevent it settling satisfactorily, thus creating air 

 pockets. When the wall is inclined inward the silage will set- 

 tle away from it. In the case of concrete silos with tapered 

 walls, these should be vertical on the inside. 



The quality of silage improves as the depth increases, due to 

 the weight above. The usual silo today is 30 or more feet 



