CONCRETE SILOS. 



25 



the same parts in both engravings. The door frames are 

 introduced in their places and held by braces until the 

 walls rise around them. 



MATERIALS USED. It is best, unless indeed some 

 one in the neighborhood has had experience, to test be- 

 forehand the proportions of sand, gravel, and lime, or 



. 3. METHOD OF LAYING THE CONCEETE. 



cement, which are best suited to the proposed work. 

 There is so much difference in the various kinds of lime 

 that proportions can only be given appr6ximately. 



Eoughly the proportions may be stated as one part lime 

 to seven parts of other materials, half of which, should be 

 clean washed sand. When sufficient materials are accu- 

 mulated upon the mixing board, they are first mixed dry 

 by repeated shoveling, then the lime, slaked to a creamy 

 consistency, is added, and well mixed through the whole, 

 adding more water if necessary. The addition of one- 

 fourth cement, the lime being reduced to three-fourths 

 of one part, and the cement being added after the mortar 

 2 



