26 



On the Principles and Methods 



[Jan., 



discharging drains b. A fair slope for this plan is from 1 in 100 to 

 1 in 120, or thereabouts. 



The catchwork system is suitable in all cases where the ground 

 has a rapid rate of inclination, as, for instance, on the side of a hill. 

 It consists of a series of carriers one above another, as illustrated in 

 Fig. 3. The sewage, flowing into the first and highest carrier, falls 

 over the intervening land between it and the next lower carrier, 

 which then takes up the water to distribute it in the same way on 

 the land below it, and so in turn the process goes on till the bottom 

 of the field is reached. 



Catchwork. 



The sewage is first received at a, and flows over the ground to 

 b, thence to c, and it is finally conveyed away by the trough or 

 carrier d. The carriers in this case may be cut at a distance from 

 each other of from 35 to 40 feet. As to the slope itself, 1 in 12 

 would be found a good limit, although 1 in 4 or 5 has not been 

 considered too steep. 



The bed system is well adapted for level lands, or where there 

 is but a slight fall. On this plan the land is laid out in a series of 

 ridges and furrows ; the sewage is admitted into carriers which run 

 along the summit of each ridge, and falls over the incline into the 

 furrow below. This will be readily understood from the annexed 

 plan and description, Fig. 4. 



a represents the ridge carriers which receive the sewage from 

 the main carriers, running at right angles to them at the head of 



Ridge and Furrow. 



the field, and b shows the carriers in the furrows which are con- 

 nected with the discharging drains. The sides of the slopes are 

 carefully levelled to an inclination of about 1 in 120, and the ridges 

 may be placed at an average distance of from 30 to 80 feet apart, 

 according to the crop put into the ground. 



