TUNNKLLTNO THKOUGTI VARIOUS STRATA. 



153 



Structed a short time ago, althonrrli only about 220 yards in 

 lenf^th, was found to bo one mass of old workings, nearly 

 from end to end ; and what was expected to have been a 

 tunnel through sound Pennant rock, and of a very simple 

 nature in its construction, turned out a very expensive pioco 

 of work, and required the most careful and costly tunnelling. 

 In some places there were great holes, some 10 to 20 feet in 

 height above the top of the tunnel, filled with rubbish ; and 

 these holes had to be most carefully timbered, and closely 

 pac]<;ed with masonry or stone, owing to the ground having 

 been so disturbed in their neighbourhood by long exposure 

 and neglect. This nearly doubled the expected cost of the 

 tunnel. Those old workings were no doubt not entirely un- 

 known in the noighbom-hood ; and probably, if the engineers 

 had made inquiries, they might liavo formed some idea as 

 to their nature and extent ; and so, what was expected to 

 have been a simple little tunnel would not have turned out 

 a very troublesome and costly one ; but the extent of tho 

 difficulty would have been known from the first and arrange- 

 ments made accordingly. This shows tho necessity in the 

 coal measures, anywhere in the vicinity of collieries or old 

 workings, of first obtaining as thorough a knowledge as 

 possible of the position of these, so that they may be 

 avoided if possible; or, if this cannot bo done, that proper 

 precautions may be taken in the first place, and the exact 

 nature of the difficulty and the cost known without its 

 coming afterwards unexpectedly in the shape of a large bill 

 for extras from tlio contractor for tho undertaking. 



Fortunately, owing to tho tunnel referred to being so 

 short, there were no shafts, and it was entirely worked by 

 bottom headings driven from both ends, so that the water 

 found blocked up in the old workings ran away by gravita- 

 tion ; otherwise, if it had been met with in shaft workings, 



