THE MORAINE 41 



plunged automatically into the same position as it 

 previously occupied, without having to consider how 

 far down it should go. 



To return to the moraine, however ; this valve, on a 

 level with the lowest part of the floor, I carefully 

 gauzed with perforated zinc on the inside to prevent 

 it by any chance getting choked up. At six to eight 

 inches from the level of the floor I arranged small aper- 

 tures in the retaining walls between the topping stone. 



It will thus be seen that when I allowed the water 

 to enter the upper compartment, the valves being 

 closed by corks, the water would trickle into the lower 

 one through the six inch overflow holes ; from this 

 it would escape in a similar way, and as immediately 

 beneath this my series of bog terraces commenced, 

 the water would supply that also ! When, however, I 

 opened the lower valves no water whatever would 

 remain in the compartments, but drain out, owing to 

 the inclined floor. 



When I was sure that this part of the scheme was 

 working satisfactorily, I proceeded to put a layer six 

 inches deep of broken brick rubble about as large as my 

 fist into the bottom of each compartment. Upon this 

 I placed a layer two inches thick of stone of the required 

 size to just cover over the interspaces between the lower 

 coarser stuff and thus prevent any finer soil from 

 sifting in between them to a serious degree. 



