240 STATE BOARD OF AGRICULTURE. 



14 inches wide and with an inside diameter of 15 feet was dug, 6 feet 

 deep. The digging of such a trench was made possible by the fact that 

 the ground here was all clay. This trench was used as a form into 

 which to build the below ground wall with the exception indicated be- 

 low. After the completion of the upper wall the earth inside was ex- 

 cavated to the depth of the wall, 6 feet, and a cement floor was laid. 



In building the wall above ground an inner and an outer form were 

 used, each 4 feet high. The inner form was made in two sections of 

 2x6 hemlock nailed to wooden half circles. One piece of 2x6 was loose, 

 to be removed to loosen the form before lifting and to bring it back 

 close to the inner surface after lifting. 



The outer from was made of 4-inch hemlock strips held together, 

 in part, by a 28 inch strip of sheet iron covering a little more than 

 the upper half of the inside, and in part by two iron hoops with turn- 

 buckles. The hoops with turn-buckles performed the further office of 

 drawing the outer form tightly against the outer surface of the wall 

 after each liting of the form. 



The outer form was set 2 feet down into the trench and properly 

 adjusted to build the upper 2' feet of the below ground part of the 

 wall. The inner form was then properly set in place and the upper 

 2 feet of the below ground wall and the first 2 feet of the above ground 

 wall was set up. From this point until the wall was completed, the 

 outer form was raised about 24 inches each time, while the inner form 

 was raised at the rate of about 48 inches, i. e., its full width. By rais- 

 ing the outer form at the rate of 24 inches each time each section of 

 wall was set up against sheet iron which insured a smoother wall than 

 could be had if set up against wood. 



Wooden forms were used to shape the openings for the doors. 



To reinforce the walls, pieces of No. 9 fence wire were built into 

 the concrete at intervals of about 1 foot. 



In sections of the wall between doors these pieces of wire extended 

 completely around the silo and were so built into the concrete. 



In those sections which were to contain doors a 4 foot piece of % 

 inch gas pipe was set up about 6 inches out from where the door 

 should be, one on each side, and so that one end of each piece stood 



6 inches above and one end of each 6 inches below where the door should 

 be. The ends of the pipes extending above the door were then tied 

 together with a few twists of wire as were also those extending below. 

 To these pieces of pipe were tied the ends of the pieces of wire which 

 were to be built into the walls of the section, and so were built into 

 place. 



The concrete used in the construction of the wall was made of mixed 

 sand and gravel, and a good Portland cement. The wall is of the 

 same thinkness from ground to plate, 10 inches, but the richness of the 

 concrete varies. The portion of sand and gravel to cement in the first 

 13 feet above gruond is 6 to 1. In the upper 13 feet the proportion is 



7 to 1. 



After completion both inner and outer surface of the wall was 

 "whitewashed" with a rich cement wash. 



The wall is surmounted by a plate made up of 4 thicknesses of y% 

 inch hemlock boards, sawed to the circle of the wall and held in place 

 by bolts built into the wall. This plate carries a roof built in the 

 same manner as that on silo 2. 



