CATTLE LICE AND HOW TO ERADICATE THEM. 



25 



from one-quarter to 1 inch in diameter. The mixing should be done 

 on a smooth, tight, platform and the sand and rock measured sepa- 

 rately in a bottomless box 2 feet long, 2 feet wide, and 1 foot deep, 

 having a capacity of 4 cubic feet. For 2^ cubic feet mark the inside 

 of the box 7^ inches up from the bottom. Each sack of Portland 

 cement is considered equal to 1 cubic foot. Mix thoroughly the sand 

 and cement, add the crushed stone (previously drenched with water), 

 and mix the whole mass by turning it several times with shovels. 

 Then add water in a depression made in the center of the pile and 

 mix well by turning several times with shovels, adding sufficient 

 water during the mixing to make a quaky or thin jellylike mixture. 



I-'IG. 14. Section of trench for concrete vat with perpendicular sides, showing the forms 

 in place and another method of bracing. (Compare with fig. 13.) 



The placing of the concrete in the forms should be commenced 

 as soon as the mixing is finished. The floor and exit end should be 

 laid first and the concrete well tamped. In filling the forms the 

 concrete should be settled into place by spading rather than tamp- 

 ing, and special attention should be given to spading next to the 

 inside forms to force back the coarse particles and allow the sand- 

 cement mortar to form a dense, water-tight surface. An old hoe 

 straightened out makes a good spading too], as the handle is long 

 enough so that the bottom of the forms may be reached. If it is 

 necessary to stop work for the day before the forms are filled, the 

 surface of the concrete in the forms should be roughened with a 

 stick. Just before placing additional concrete wash the roughened 



