302 ox LANDSLIPS. 



— an easily grafted material, but the most slippery stuff I 

 have ever had to deal with. 



The result naturally following the use of such a material, 

 put together by barrow-work during such a rainy time, was, 

 that when the line was ready to be opened in 1841, a number 

 of serious slips had taken place in this bank ; but they were 

 all on the eastward side of it. So it was decided .0 lay the 

 permanent way only upon the western side of this bank, and 

 to work the traffic there upon a single line (the rest of the 

 line being double) until we had cured the slips upon the east 

 side. 



The largest of the slips were about 110 yards in length ; 

 breaking away, on top, from near the middle of the bank, 

 and, at bottom, carrying forward the recess (or '' cess " as the 

 men called it) along with them. Thus the total perpendicular 

 depth of the slips was 40 feet. The clay was, in fact, sliding 

 back into the side-cutting from which it had been dug, and 

 carrying forward the " cess " with it. The ''cess " preserved 

 its level, but was shoved gradually forward into the side- 

 cutting — fastest in the central parts, and more and more 

 slowly towards the ends. Here it ma}^ be well to describe 

 the " slipping surface," a most important feature, with which 

 I afterwards became familiar. I found that slips always 

 form a conchoidal " slipping surface," nicely lubricated, and 

 as smooth and polished as the inside of a marine shell, on 

 which the mass slides slowly downwards. By digging down 

 into the slip this " slipping surface " is always readity de- 

 tected, the material naturallj'' breaking away from it. Its 

 vertical form is alwa^'-s conchoidal ; starting from a nearly 

 upright face on top, it forms a graceful curve down to a 

 nearly level surface at bottom. 



"When the time came to decide upon what should be done 

 to stop these slips, Brunei came down, and, after inspecting 



