1869.] The Projected Mersey Tunnel and Baihvaij. 185 



The aliove amoimt spread over the 3520 hneal yards of heading 

 gives 21Z. lis. as the cost of each hneal yard, and deducting 

 therefrom 11., the value of the additional excavation, centering, and 

 brick-lining (not found necessary in tunnels in the red sandstone), 

 it will bring the price per lineal yard to 14Z. lis., without taking 

 into account the more than double value of labour at Chicago, 

 which has unfortunately greatly augmented the outlay upon this 

 ■work. 



Now 20,000?. expended upon 1800 lineal yards of heading under 

 the Mersey gives the price for each 15Z. 5s., so that, in drawing a 

 comparison between the two works, a greater sum has been taken 

 in the estimate for the one than has been actually expended on the 

 other, and this is assuming the price of labour to be the same in 

 both instances, which, however, is by no means the case, that at 

 Chicago being very high. 



I may here allude to a very interesting and instructive work, 

 also very analogous to that prop.osed under the Mersey, which has 

 been carried to a satisfactory conclusion at Attock, on the Khyra- 

 bad Pass, in India. 



It consists of a heading 600 yards long, 6 feet square, driven 

 under the river Indus through a rock, which forms its bed, at a 

 depth of somewhat over 90 feet below the surface of the flood- water. 



It has been carried on by a few labourers, under the charge of 

 Mr. Eobinson, who have succeeded in filling up the fissures they 

 met with during the operation by simple " feather " wedging of 

 wood, and have by this expedient been able to keep back all the 

 water which otherwise would have flowed into the heading with a 

 force due to the whole superincumbent column. 



The cost of this work has been about 13,000/.. and spreading 

 the whole outlay over the 600 yards, brings out the cost to about 

 21/. 14s. per yard, which goes to prove that, had the labour ex- 

 pended upon it been paid for only at English prices, it would have 

 been executed at a considerably smaller cost than that arrived at by 

 estimate for making the heading under the Mersey. 



I have lately constructed a water-level, nearly one-third of a 

 mile long, through harder rock, yet far less compact and more 

 broken up, having much larger feeders of water than any to be 

 expected in the red sandstone. In driving this heading and the 

 shafts connected therewith, single feeders were met with yielding 

 1,000,000 gallons per diem, yet these were dealt with without 

 serious diflSculty or expense, the cost not having been one-half that 

 estimated for the Mersey work. 



In driving the heading a boring-rod would, as is usual in water- 

 bearing strata, be kept ahead of, and at the top of, the work, and 

 thus due notice would at once be given of any unusual feeder of 

 water, should such exist. 



