532 



Journal of Agriculture. 



[lo Aug., 19 io. 



14? 



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lbs. ; as a gallon of water weighs 

 10 lbs., the proportionate bulk of 

 void spaces is thus arrived at. 



Great care should be taken in 

 the selection of materials. The 

 metal or gravel should be fairly 

 strong, soft sandstones and lime- 

 stones being avoided. The sand 

 should be clean, sharp and coarse. 

 Clay and loam intermixed are seri- 

 ous drawbacks. Most brands of 

 locally-made cement are reliable. 

 A cask of cement contains slightly 

 more than four cubic feet. As a 

 rough and ready rule, one barrel 

 of cement goes to the cubic yard 

 of concrete. It must be borne in 

 mind that practically one cubic 

 yard of gravel or metal is required 

 for one cubic yard of concrete, the 

 cement and sand serving only to 

 fill up the voids. For mixing, a 

 platform or smooth space is re- 

 quired. The sand, which should 

 be dry, is first put on the mixing 

 board and then the cement is 

 added. The two are thoroughly 

 mixed by being turned over with 

 shovels. The metal is then added. 

 jNIixing by shovelling is thoroughly 

 done, after which water is added ; 

 a watering can with a rose is best 

 for the latter purpose. Shovelling 

 is continued until the whole mass 

 is sufficiently wetted, that is, when 

 it is in a pasty condition, but not 

 enough so as to run or be sloppy. 



Concrete must be used immedi- 

 ately it is mixed. Care should be 

 taken in ramming not to keep it up 

 longer than the commencement of 

 setting, a matter of a few minutes 

 only. Any old work, including 

 that finished the previous day, 

 should be well wetted before add- 

 ing fresh concrete. Except in very 

 moist weather, the concrete should 

 be kept damp by wetted bags or 

 other means for a few days to 

 allow the setting action to proceed 

 properly. With the exception of 

 the floor of exit slope, the concrete 

 should have a smooth surface. To 



