i882. 157 Trans. N. V. Ac. Scz. 



nineteen feet in width by twenty-four in height. The whole would be 

 lined with brick ; but this brick wall and arch would not be quite in 

 contact with the chalk excavation, but a space was to bs left between, 

 to allow any percolating water to pass down without entering the tun- 

 nel-way and escape beneath its floor. This escape would be secured 

 by the slope of the tunnel, which is to be highest at the middle and de- 

 scending somewhat toward each end, where large reservoirs will be 

 excavated for any accumulating water, which will thence be removed 

 by powerful steam pumps, raising it through shafts to the surface. The 

 important matter of ventilation is ro be provided for by engines at 

 either extremity, so working as to insure a steady and powerful current 

 of air through the entire tunnel, one pumping air, and the other ex- 

 hausting it. 



The machinery employed in the work of excavation was also referred 

 to and illustrated ; but it is peculiar and complicated, and cannot be 

 well described, save at length and with figures. In working through 

 the comparatively soft chalk, the process is strictly one of cutting ; and 

 a very ingenious and beautiful machine is employed, wherein a series 

 of blades, like knives set upon revolving wheels, is made to cut the 

 chalk at the extremity of the boring. The machine itself is also ad- 

 vanced on wheels, as it works onward the heading from day to day. 

 Thirty-six feet is about the daily rate of progress ; and it is computed 

 that the whole will be finished in five or six years. 



Estimates were then given of the profits which it is expected will be 

 realized, if the work is successfully completed. The amount of funds 

 requisite to do this will be forty to fifty millions of dollars ; say, ten mil- 

 lions of pounds sterling. Three-fourths of the present passenger traf- 

 fic should, it is altogether probable, prefer the tunnel to the channel 

 voyage ; and, considering the advantage in freight-transit of not " break- 

 ing bulk " for shipment, the receipts may be estimated roughly as fol- 

 lows : 



Passenger travel ^850,000 



Freight ... 300,000 



Mail service, etc 50,000 



Total _£i, 200,000 



Deducting from this, say, forty per cent, for expenses (;^ 480,000), or 

 somewhat less, there will remain a profit of ^720,000, or more, which 

 would yield from seven to seven and a half per cent, yearly on the cap- 

 ital of £10,000,000. If this capital seems large, it is not so in compar- 

 ison w.th the sum already invested in the English railways, which 

 amounts to about ^700,000,000. 



For his own part, the lecturer was fully convinced alike of the need. 



