32 SILOS: CONSTRUCTION AND SERVICE 



roof for the masonry silo is masonry. It is easy to build it 

 either of concrete or clay products, and then it becomes fully 

 as permanent as any other part of the silo. 



Stone Silos. The use of stone silos is naturally confined 

 to localities where stone is plentiful; and probably the great- 

 est number of these stone silos are to be found in Wisconsin. 

 The cost of material under favorable circumstances is very 

 slight, in fact almost nothing when it must be gathered from 

 the field to permit cultivation. The labor feature is an 

 important factor, and as the cost of labor increases, the 

 building of stone silos decreases. 



It was common to depend upon very thick walls to with- 

 stand the outward pressure, but, as already stated, it is never 

 safe to depend upon masonry to withstand any force which 

 tends to pull it apart. Where liberal amounts of steel have 

 been placed in the wall they have not cracked, and where 

 they have been plastered inside with a good cement plaster 

 they have made very satisfactory silos. 



Concrete Silos. With the advent of concrete, and 

 especially reinforced concrete, it was only natural that it 

 should be tried for silos. It has been used in many different 

 ways in monolithic construction (molded in place in forms) 

 with both single and double wall, and is also made into silo 

 blocks of different kinds. It is difficult to say just who was 

 the first to use concrete for silos, or even in which section of 

 the country this use of concrete originated. But today it is 

 successfully and very widely used. 



Like the stone silo, the advisability of using it depends 

 very largely upon the supply of material; that is, gravel or 

 crushed stone. It has been found durable for all climates, 

 is storm proof and fire proof, in fact it is difficult to see how 

 anything could be built more permanently. Double walls 

 are advantageous in resisting frost. This form of construe- 



