AGRICULTrRAL ENGINEERllTa 



155 



Capacity of Cisterns in Barrels, Per Foot in Depth. 



(Hall.) 



Square Cistern. 



Barrels. 



5 feet by 5 feet holds 5.92 



*; 8.54 



" 11.63 



" 15.19 



" 1939 



23-74 



Circular Cistern. 



5 feet in diameter holds. 



6 " " 



7 " " " " 



8 '• " " " 



10 '• " " " 



Barrels. 



... 4.66 

 ... 8.54 

 ... 11.63 

 ... 15-19 

 ... 19.39 

 ... 23.74 



ROAD-MAKING. (Campbell.) 



Drainage. — Perfect drainage, first of the foundation of 

 the roadbed, secondly of the road surface, are the points 

 in road-making on which too much stress cannot be laid. 



The first is accomplished by underdrainage, tile drains 

 being laid at a depth of three or more feet below the sur- 

 face on each side of the roadbed at the foot of the grade 

 and parallel to it. Care should be taken to fit and settle 

 the tile in the trench so that, when refilling with earth, 

 they will not be displaced. As a rule 2|- to 4-in. tile will 

 be sufficient. The joints should be close, and the grade 

 a true line. Loose joints and an uneven grade allow silt to 

 pass into the tile and remain there, destroying the drain. 



Surface drainage is accomplished by open drains on each 

 side of the grade, having sufficient capacity to drain, both 

 the roadbed and the land adjoining. With open drains and 

 with tile drains make and maintain a free outlet to the 

 nearest watercourse. A drain without an outlet is useless. 



Crowning the Road. — The graded portion of the road 

 should be wide enough to accommodate the travel upon it, 

 and not greater, the slope being uniform, not heaped in 

 the centre. The crown should be well above the overflow 

 of storm water, and should have a grade sufficient to shed 

 water readily to the open ditches on either side. Do not 

 round it up so as to make the grade steep and dangerous, 

 under the mistaken impression that better drainage will 

 thereby be secured. Nor should it be so low as to allow 

 water to stand upon it in depressions. Under ordinary 

 circumstances one inch or one inch and a half to the foot is 



