309 
who must compete with all other makers of like material ; but 
the sand and gravel constituting one-third or one-half of the final 
product must be selected and prepared by the farmer, and this is 
where most failures originate. Various amounts of each are 
used, according to the use to which the finished product is to be 
put. The mixture in which all the spaces or voids between the 
stones or gravel are filled with sand and all the spaces between 
the grains of sand are filled with cement is the ideal mixture. The 
ideal is seldom attained, but the bulletin gives detailed instruc- 
tions and instructive illustrations, which should go far toward 
enabling the farmer to closely approach it. 
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