Construction o All-\V(,cd Silos. 417 



not extremely severe, or if the silo is only to be fed from 

 in the summer, it would be better to do away with the layer 

 of sheeting and paper outside, putting it on the inside, thus 

 securing two layers of paper and three layers of boards for 

 the lining with the equivalent of only 2 inches of lumber. 



516. Construction of Hoof. The roof of cylindrical silos 

 may be made in several ways, but the simplest type of con- 

 struction and the one requiring the least amount of mater- 

 ial is the cone, represented in Figs. 202 and 205. 



If the silo is not larger than 15 feet inside diameter no 

 rafters need be used,, and only a single circle, like that in 

 the center of Fig. 205. This is made of 2-inch stuff cut 

 in section in the form of a circle and two layers spiked to- 

 gether, breaking joints. 



517. Ventilation of Silos. Every silo which has a roof 

 should be provided with ample ventilation to keep the 

 underside' of the roof dry and in the case of wood silos, to 

 prevent the walls and lining from rotting. One of the 

 most serious mistakes in the early construction of wood 

 silos was the making of the walls wkh dead-air spaces 

 which, on account of the dampness from the silage, lead to 

 rapid "dry rot" of the lining. 



In the wood silo and in the brick lined silo it is important 

 to provide ample ventilation for the spaces between the 

 studs, as well as for the roof and the inside of the silo, and 

 a good method of doing this is represented in Fig. 207, E, 

 where the lower portion represents the sill and the upper the 

 plate of the silo. Between each pair of studs, where needed, 

 a one and one-fourth inch auger hole to admit air is bored 

 through the siding and sheeting and covered with a piece 

 of wire netting to keep out mice and rats. At the top of 

 the silo on the inside the lining is only covered to within 

 two inches of the plate and this space is covered with wire 

 netting to prevent silage from being thrown over when 

 filling. This arrangement permits dry air from outside to 

 enter at the bottom between each pair of studs and to pass 



