l<;o EG YPTIAJS AGRICULTURE. 



better to dig a larger channel in order to get more earth 

 for banks, and afterwards it can be allowed to silt up and 

 reduce its sectional area to proper dimensions. 



Slopes of banks must be ruled by the nature of the soil. 

 Drains not carrying much water, and the smaller canals 

 not running constantly may have steeper slopes, for, if a 

 bank docs slip in, the obstruction is easily cleared. With 

 larger canals and drains risks must not be incurred, and 

 safe slopes should be given from the first. 



Roads are not made to full width at first, but space is 

 left for widening them with soil thrown out in annual 

 clearances. Besides, banks sink and broaden out and when 

 sufficient width has been attained the fellaheen may be 

 allowed to remove the canal silt clearances to top dress 

 their fields, and this they very readily do. 



It will be noted that in calculating sectional area, only 

 the excavated area is taken, although canals usually carry 

 water above ground level. But the berm of the canal soon 

 grows weeds which obstruct the current, and the area of 

 channel above the berm has no carrying capacity. The 

 central area above ground level has carrying capacity but 

 is set against irregularities and obstructions which soon 

 appear in the channel. 



Canals arc dug of sufficient section to afford soil for 

 making banks, which should be strong enough to keep in 

 the water, and wide enough for paths or roads to give 

 easy access to the fields. All canals which hold water 

 permanently up to ground level must have infiltration 

 drains to intercept the leakage, which would otherwise 

 waterlog the soil alongside the canal and greatly deteriorate 



