144 



ENGINEERING ON THE FARM 



an advantage in cold weather, but owing to the difficulty 

 of tamping there are more chances for air space or unfilled 



Fig. 139. Use of a mixing box; a method that will not give as good 

 results as ihe use of a mixing platform 



Fig. 140. Equipment used in concrete mixing 



portions that will show up when the forms come off. For 

 these reasons a too dry mixed concrete or mortar is not 



