against a bridge. Although neither political nor military ob- 

 jections against the North Channel Tunnel scheme are tenable, 

 yet the engineering difficulties are stupendous, and much 

 greater than those anticipated in the proposed English Channel 

 Tunnel, whilst the anticipated traffic is considerably less. 



In order to compare the " Submerged Bridge " scheme 

 with the tunnel schemes, I have drawn sections of the North 

 Channel (Fig. 2), shewing four of the principal proposed routes 

 for a tunnel. How many more routes have been suggested it is 

 difficult to ascertain ; they are numerous no doubt, and leading 

 from as many points in Ireland to as many in Scotland, each, 

 in the opinion of its advocate, presenting some special advantage. 



Section a (Fig. 2) represents the contour of the channel 

 bottom between Donaghadee and Portpatrick, a distance of 19 

 nautical miles. This route was preliminarily surveyed and 

 favourably reported upon by an engineer now deceased. 



Section b is that between the Great Copeland Island and Port- 

 patrick, land to land 17% miles, plus f mile of channel between 

 the mainland and the island. Considerable advantages present 

 themselves in this route, viz : the reduction of the distance 

 between the working shafts by \\ miles, which would reduce the 

 distance the debris would have to be conveyed during construc- 

 tion : additional working shafts could be constructed at the 

 Irish end, thereby increasing the number of working faces, 

 and shortening the distance between the nearest ventilating 

 shafts ; all important considerations to engineers. 



In these two Sections, a and 3, there is a considerable 

 depression nearer the Scotch than the Irish coast, at which the 

 greatest depth is 890 feet ; this would involve exceptionally 

 steep gradients, difficulties in pumping and ventilation, and 

 an extraordinary expense and length of time : — matters quite 

 beyond the object and scope of this paper, 



Section c is that between Whitehead, or Blackhead and Port- 

 patrick, a distance of 22 and 21 miles respectively. The 

 shallowness of the channel in this route is its special recom- 

 mendation, the greatest depth of water being 650 feet. 



