4o6 



Journal of Agriculture. 



[8 July, 1907. 



bv the company for the same price and under similar conditions to the 

 wood and iron silos put up by the Department of Agriculture. The blocks, 

 in order to fit in with the circular plan of the accepted form of silo, had 

 to be somewhat modified in form and special " bearing off " boards were 

 required. The gravel and sajid already mixed were obtained locally. 

 Screening was necessary to remove pebbles much over half-an-inch. The 

 blocks were readily made by some of the boys at the Orphanage though 

 their weight, a little over 50 lbs., was rather great for the boys' strength. 

 A ring of cement concrete 12 inches wide and 6 inches bedded upon sand 

 was set down as a foundation for the silo which was 16 feet and 15 feet 

 6 1 inches, outside and inside diameter respectively, and 21 feet in height. 

 Portholes, 3 feet by 2 feet, were put in at every 3 feet of height, making 

 three in all. These were framed in 6 bv i Oregon. Doors were made 



• ■ -'■"■■ ........^.-. ^v :'''"-Tn TiiiaiiiiiiinwHiirri ■"■■■■-■ 



THE CONCRETE SILO. LAVING THE SECOND COURSE. 



of Xo. 24 gauge iron which was lapped over the edges of the portholes 

 and stiffened with three 6 by i boards, the latter resting against the frames. 

 In order to strengthen the wall against the outward thrust or pressure of 

 the silage, five bands of 2 inches bv one-sixteenth of an inch hoop iron, 

 with lugs bolted on to ends and tightening bolts, were put round the out- 

 side of the silo' at everv second course up to the tenth. Thus for half the 

 height of the silo, every block has some support from the hoop. Above 

 these the pressuie is too slight tO' need much precaution. The hoops are 

 kept in place bv bent iron hooks or holdfasts built into the wall as shown 

 in the illustration on page 404. Where the hoops pass in front of the 

 porthole doors, thev can be slackened and let down OLit of the wav when 

 the portholes come into use, as the diminution in the contents bv that time 

 would have removed any outward pressure. While in course of con- 

 struction, however, a departure from the hoop-iron reinforcement or 



