26 Concrete Silos 



these separately and determine the grounds of its 

 importance. 



(1) Airtightness. It is quite customary, as we 

 have already done in the first chapter of this volume, 

 to liken a silo to a giant fruit jar. And whether can- 

 ning is being done in the home or on an extensive com- 

 mercial soale in a canning factory, it is recognized as 

 of prime importance that the contents of the can shall 

 be sealed positively from the air. For this purpose a 

 material which is absolutely airtight is used glass in 

 one instance, and tin in the other and the seal is made 

 in one case with a rubber gasket and in the other with 

 a solder joint. The demand for the exclusion of air 

 has a perfectly well recognized scientific basis. The 

 spoiling of fruit or vegetables in a can, or the spoiling 

 of silage in a silo by rotting, is simply a bacteriological 

 action and will not take place unless oxygen be pres- 

 ent to support the organisms which destroy the con- 

 tents of the receptacle. 



(2) Imperviousness to Moisture. It is necessary 

 that the walls of a silo be impervious, not only to ex- 

 clude moisture from the outside, which at times might 

 enter in such quantities as to do considerable damage 

 to the contents, but also to preclude the possibility of 

 the natural juices in the silage from being lost. As 

 previously pointed out, one of the advantages of silage 

 is the fact that these juices are retained rather than 

 being allowed to evaporate, as in the case of ordinary 

 hay. So the silo which approaches closest to the ideal 

 will be the one which retains the contents in as nearly 

 its original condition as possible. 



(3) Fireproof ness. In addition to the value of the 

 silo itself, the contents of the silo can perhaps be 

 taken at a value of about $5.00 per ton as an average 



