TENTH ANNUAL YEAR BOOK— PART X 1 



No. 4 type of foundation is shown in Fig. 15. Earth is utilized for 

 the outer form, but lumber is used for the inner. By permitting this 

 to extend down only to within a few inches of the bottom of the pit, 

 the footing may be permitted to widen. This is desirable, as a wall 

 need never be as thick as the width of the footing. In case the ground 

 is reasonably level and firm, it will be cheaper to simply dig a narrow 

 trench and widen same at bottom to 16 inches. If ground is excavated 

 next day and concrete trimmed, a reasonably smooth job is insured. 



Note: Additional braces for inner 

 form are necessary. 



f 



FORMS FOR MAKING CONCRETE FOUNDATION 



Fig. No. 15. 



THE FLOOK. 



Under certain conditions, the silo floor may be dispensed with without 

 interfering with the preservation of the silage. Where the silo rests 

 upon dry clay or any non-porous soil, and where the foundation is deep 

 enough to prevent undermining by rats, the floor may be omitted. Usually, 

 however, a floor is desirable. The portion of the silo below the ground 

 may be made more nearly water tight, the floor may be thoroughly 

 cleaned, and there is no mixing of earth with the silage. A silo floor 

 need not be thick or expensive, as the weight of the silage, though -very 

 great, is evenly distributed over the surface and would be just as 

 firmly supported if the floor was not used. A concrete floor of the usual 

 sidewalk construction, three to four inches in thickness, will be very sat- 

 isfactory. If properly graded, sand and gravel can be obtained, one 

 part of cement to five parts of sand and gravel will be about the right 

 proportion to use. The concrete should be thoroughly tamped and 

 troweled. 



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

 to use a clay sidewalk block or even a hollow block, the same as used 

 in the wall, covered with thin coat of plaster. In the case of the side- 

 walk blocks, the plaster 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 WAIX. 



The first consideration in the wall is the selection of the material. 

 The material used in the Iowa silo as originally designed was rectangular. 



