26 SILOS AND ENSILAGE. 



is mixed, makes a much quicker setting and harder con- 

 crete. When all cement and no lime is used, but a small 

 quantity can be mixed at a time, for it sets so quickly 

 that it could not be placed in position before it became 

 solid. The proportions for a smooth, solid concrete are : 

 one part Portland cement to five parts sharp sand. If 



Figs. 4 and 5. RAISING THE PLANKS. 



mixed rather liquid, one-third or more, often nearly or 

 quite two-thirds, of the wall as completed, may consist 

 of gravel and coarse broken stones, put in while the 

 cement is being placed in the molds forming the walls. 



WHITMAN & BURRELL ON CONCRETE SILOS. 



These gentlemen, in their paper on silos, given else- 

 where, append the following directions for construct- 

 ing a silo of concrete : First, having excavated for the 

 silo, dig a trench all around the bottom and fill in 

 with cobble stones, and from one corner lead a drain, 

 if possible, so as to carry off all water. The trench 

 under the proposed walls of the silo being filled with 



