THIRTY-FIFTH ANNUAL CONVENTION. 283 



spect. In regard to the concrete neutralizing the acidity of the 

 silage, it may be stated that for such a thing to take place 

 there must be enough moisture present to permit the dissolved 

 cement to diffuse itself throughout the acid solution. The 

 amount of moisture present renders this action quite impossi- 

 ble. Concrete silos were found in actual use which had been 

 filled eleven times without any noticeable action of the acidity 

 of the silage in softening the walls. These silos were not 

 coated with a cement wash, but it is considered good practice 

 to paint the walls on the inside with cement every two or three 

 years. A coat of coal tar has been used successfully by some 

 silo owners for the same purpose. This painting may be clone 

 while filling if the walls have been swept down well as the 

 silage is fed out. 



Among the desirable features of the concrete silo or any 

 masonry silo may be mentioned that it is essentially fire-proof. 

 A silo was found in use in Wisconsin which had withstood a 

 fire that burned all the surrounding buildings. 



Single and Double Wall Concrete Silos. 



The single wall concrete silo is the most common style of 

 construction. The thickness of the walls of silos now in use 

 varies from 6 inches at the bottom to four inches at the top 

 for the lightest wall to a wall two feet in thickness, which is 

 the heaviest of which the Section has record. Six inches 

 seems to be the most desirable thickness for common sizes of 

 silos under existing practice. The walls might be made 

 lighter at the top, but the saving of material would hardly 

 balance the trouble of varying the size of the forms. The 

 double wall concrete silo at present is made only with a pat- 

 ented form. The inner wall is 5^2 inches thick, the outer wall 

 %y 2 inches thick, and the two tied together with steel ties with 

 a three-inch air space between. Circulation is prevented by 

 inserting horizontal tar paper partitions every Z]A feet. This 

 construction, besides being as satisfactory as the single wall 

 method, places it entirely above any criticism in regard to freez- 



