BUILDING THE SILO. 317 



far up from the plates, they assist materially in pre- 

 venting the silo from spreading. But there is no 

 necessity for nailing them tluis to each pair of rafters. 

 The covering of the roof may consist of boards and 

 shingles, or indeed, of any of the materials used in 

 covering roofs that may be desired. In the gable 

 should be a hinged door to admit green food when 

 the silo is being filled. It should be not less than 

 two and one-half feet wide to admit carriers such 

 as are commonly used when silos are being filled ; 

 but sometimes the gable end is left open. There 

 should also be at least one cupola or ventilator on the 

 ridge of the roof to furnish egress to the gases which 

 are generated by the fermentation of the silage. If 

 the roof of a silo is closed tightly, premature decay 

 in the roof would result. 



BUILDING STONE SILOS. 



It is almost certain that the stone silo will grow 

 in favor with the passing of the years because of its 

 greater relative duration. This will at least prove 

 true in localities abundantly supplied with stone. 

 The greater relati^-e first cost of constructing stone 

 silos is probably more than anything else responsible 

 for the infrequency with which such silos are found. 

 Future experience, however, is likely to show that 

 when the greater duration of stone silos is taken into 

 account, they will prove the cheapest by far in the 

 end. The objections have been brought against 

 them that they are damp, and that frost easily pene- 

 trates them,, and both objections are true in the 

 absence of certain precautions when building them. 



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