60 WALTER SHELLSHEAR. ON THE TREATMENT OF 



in a sodden state, which in conjunction with the large amount of 

 pipe clay in the soil gave it every opportunity to slide out under 

 the superincumbent weight. In many places it was found that 

 the shale had been broken up for a considerable depth by the action 

 of the slip, the water having found its way into the pipe clay veins. 

 One point of importance may be noticed in connection with the 

 soil immediately above the shale and it is this, that when charged 

 with water it had the consistency of porridge and would not carry 

 its own weight, but when dry it set very hard and required a 

 pick to shift it. From the above it was evident that for the drains 

 to be successful it was necessary to lead the water off from the 

 strata immediately above the shale and to get rid of it as quickly 

 as possible so as to prevent it eroding the shale, and at the same 

 time a niter was necessary to prevent the drains getting choked 

 with slurry. 



The drainage works were carried out as follows : — An open cut 

 was made starting from the edge of the cliff, the cut being 4 feet 

 6 inches wide. The shale was cut into a succession of steps to give 

 a good footing for the rubble stone with which the drains were 

 eventually filled, a channel sufficiently wide to let in a 12 inch 

 earthenware pipe being cut in the centre so that no lodgment of 

 water could take place at the different steps, and earthenware pipes 

 were carefully laid in this channel but the joints w r ere left open to 

 freely admit the water, the use of the pipes being to prevent the 

 soft shale from being eroded by the action of the water. The 

 difficulty of opening out these cuts can be well imagined, when it 

 is remembered that in some of them there was something like 

 20 feet of moving soil upon the top of the rock. When a length 

 of about 30 feet had been opened out and securely timbered, the 

 pipes were laid and rubble stone carefully hand-packed round them, 

 the cut was then tilled up with hand packed stone to within 3 feet 

 of the surface, small fascines of brush wood being packed in 

 between the soil and the stone to prevent silting up, and fascines 

 were laid upon the top of the stone, selected soil then being filled 

 up over the drains to surface level ; this completed, another length 

 was taken out and treated in the same way until the foot of the 

 enbankment was reached, after which the drains were continued 

 as drives under the enbankment, the whole being filled with stone 

 and fascines as above described. To drain off the water from the 

 drives a series of holes were drilled through the roof until the water 

 was reached. There are eight cuts in all, (See fig. 2) four were 

 taken through the bank and ended in shafts at the high side which 

 were filled up within 3 feet of the surface with rubble stone and 

 finished off with fascines and a layer of about 2 feet of puddle to 

 keep out the surface water. (Fig. 3.) Two were taken nearly to 



