Some Tunnelling Feats 61 



hard-working steam locomotive. The main 

 reason for this inclined tunnelling is to 

 drain away quickly any springs or perco- 

 lating water. If the easier task of cutting 

 the tunnel upon a perfectly level gradient 

 were pursued there would be constant 

 trouble encountered from water, both dur- 

 ing boring and after completion. 



Although water may be the worst enemy 

 there are several others, not the least being 

 a proper ventilation system. Important for 

 the finished tunnel, it is even more so 

 during construction otherwise the workers 

 would be overcome, or, at the best, their 

 working hours at the face of the excavation 

 would be seriously cut into. 



Another uncertainty is the nature of the 

 strata through which the tunnel is driven. 

 This is impossible to determine in the case 

 of mountain tunnels, and endless trouble is 

 occasioned through this uncertainty. 



In the early days of railways, particularly 

 abroad, the engineers responsible would 

 gladly take a circuitous route rather than 

 bore through a mountain range. The 



