224 



Illinois State Dairymen's Association. 



Pi-y\TE 



i-r 



5' -6" 



4'o" 



30'-0" 



M EIGHT or OPEMinGS 



parts of good sharp sand. Two coats of 

 this mortar were used, making the plaster a 

 full half-inch thick over the lath. The sec- 

 ond coat extending continuously from the 

 bottom of the brick work to the top of the 

 silo, uniting the foundation, and the super- 

 structure and giving an air-tight wall for 

 the entire silo. 



Four doors were made of two thick- 

 nesses of common flooring run in opposite 

 directions, with tar paper between. These 

 doors are each 20 inches wdde, 2}^ feet 

 high, and are four feet apart. The top of 

 the upper door is five feet below the 

 plate, but by the time the silo is opened 

 the silage has usually settled nearly 

 to the top of the upper door, so that but little 

 silage has to be removed before the door can 

 be taken out. The size and location of the 

 four doors are shown in Cut 19 and a section 

 of one of them in Cut 16. 



Authorities on silo construction have er- 

 roneously stated that for silos 20 feet in 

 diameter and 30 feet deep, three thicknesses 

 of half-inch lumber are required to give suf- 

 ficient strength. This silo is 30 feet in height 

 above the foundation, and as the pressure of 

 silage at this depth is 330 pounds per square 

 foot there is a tensile pull on the sides of the 

 bottom foot- of a silo of these dimensions of 

 3300 pounds. In this lower foot to resist 

 this strain, there are, of course, two boards 

 each one-half inch thick and six inches wide, 

 making a total area of six square inches of 

 lumber. On account of the great tensile 

 strength of wood it was thought that this 

 one layer of half-inch lumber would be suf- 

 ficient to withstand the strain. To determine 

 if this were "true, the silo as shown in Cut 15 



