324 ILLINOIS STATE DAIRYMEN'S -ASSOCIATION. 



gravel can be obtained, one part of cement to five parts of sand 

 and gravel will be about the right proportion to use. The con- 

 crete should be thoroughly tamped and troweled. 



In some cases where sand and gravel are expensive, it may 

 be cheaper to use clay sidewalk block or even a hollow block, the 

 same as used in the wall, covered with a thin coat of plaster. In 

 the case of the sidewalk blocks, the plastering covering would be 

 unnecessary if the blocks were laid in cement. The floor should 

 be slightly hollowed in the center as a matter of economy and 

 convenience. 



The Silo Wall. 



The first consideration in the wall is the selection of the ma- 

 terial. The material used in the Iowa silo as originally designed 

 was rectangular, hollow, clay building blocks, such as have been 

 commonly used extensively in important buildings for years. It 

 was originally designed with a plaster coat of cement mortar 

 both inside and outside. However, the experimental silo was not 

 plastered either inside or out but simply washed on the inside 

 with a cement wash and, for the time it has been used, it has been 

 entirely satisfactory, indicating that the plastering is not neces- 

 sary where a tile block is used which will resist the weather. In 

 fact, only two of the silos in the bulletin have been plastered. It 

 is to be noted that the durability of this silo will depend directly 

 upon the quality of the blocks. Soft blocks which have not been 

 properly burned should be guarded against. On the other hand, 

 good vitrified blocks are among the most reliable and durable of 

 all building materials. 



It would be diflficult to overestimate the advantages of curv- 

 ed blocks. The only spoiled silage found near the walls of silo 

 No. I was a slight amount not exceeding one to four cubic feet 

 or .01 to .06 of one per cent of the total amount. This spoiled 

 silage was found in the recesses of the wall, which was quite 

 rough due to the use of long 16-inch straight blocks. A work- 

 man lays up the curved block more rapidly, and with more satis- 



