402 Rural Architecture. 



498. Walls. In cold climates it will be best to make the 

 lower portion of the wall, up to within 10 feet of the top, 

 with a 2-inch dead air space, using three courses of brick, 

 thus making the wall 14 inches thick, for all the smaller 

 and medium sized silos. If the silo is to exceed 24 feet 

 inside diameter the lower third of the brick wall should 

 be made of four courses of brick and 18 inches thick, 

 the second third 14 inches thick, and the upper third 8 

 inches, solid. The dead air space should be next to the 

 outside and this course of brick should be tied to the inner 

 wall as frequently as necessary to make it stable. 



499. Strengthening the Walls. The tendency of the 

 pressure of the silage to crack the walls of round silos in- 

 creases with the depth and with the diameter of the silo. 

 The tendency of the silage to burst a silo 26 feet inside 

 diameter is twice as great as in one 13 feet in diameter and 

 the same depth, and this makes it necessary to strengthen 

 the walls of the larger brick silos. In all brick silos there 

 should be an iron tie rod bedded in the wall, in the manner 

 illustrated in Fig. 198, between each of the lower doors to 

 compensate for the weakening caused by the doors; and in 

 the larger silos these ties should extend entirely around the 

 silo in the manner shown in Fig. 198. 



500. Wetting Brick. It is very important in laying the 

 brick for a silo wall that they should be wet and especially 

 if the work is done in hot, dry weather. If this is not done 

 the brick will so completely dry out the mortar that it can- 

 not set properly and become strong. 



501. Making Walls Air Tight. There are several ways 

 in which this may be done, and some of these will be given 

 in the reverse order of their effectiveness. 



1. After the wall is finished it may be simply given two 

 coats of thick cement whitewash, and this repeated every 

 two or three years as the acid of the silage dissolves it away. 



2. The face of the brick wall may be given a good, rich 



