MECHANICS AND USEFUL AKTS. 31 



TUNNEL UNDER THE ENGLISH CHANNEL. 



Mr. Hawksliaw has been engaged in making trial boi'ings with 

 a view to develop a project for a railway tunnel under the chan- 

 nel between Dover and Calais, and communicating on the Eng- 

 lish side with the Cliatham and Dover Railway, and on the 

 French side with- the Northern Railway of France. He proposes 

 to cai'ry on the excavations for the tunnel from both ends, and 

 also from shafts in the channel, at the top of which powerful en- 

 gines will be erected for pumping and winding up the excavated 

 material, and for supplying motive power to the machinery by 

 which the excavation is effected. 



On the other hand, Mr. Geoi'ge Remington is of opinion that a 

 tunnel on the site jjroposed by Mr. Hawkshaw is impracticalile, 

 on account of the difficulty he anticipates in keeping down the 

 water in a chalk excavation of that magnitude. He therefore 

 proposes another line for the tunnel between Dungeness and 

 Cape Grisnez, which, entirely avoiding the chalk, passes through 

 the Wealden formation, consisting chiefly of strong clay. The 

 tunnel would be twenty-six miles in length from shore to shore. 

 On this route in mid-channel, there is an extensive shoal, with 

 only eleven feet of water upon it at low-water spring tides, where 

 Mr. Remington proposes to construct a shaft protected, by a 

 breakwater. 



CHICAGO RIVER TUNNEL. 



A tunnel has recently been commenced at Washington street, 

 on the south branch of the Chicago river. It is to consist of three 

 passage-ways, the centre one to be used by foot-passengers and 

 the two side ways to be used for vehicles. The middle passage 

 will be 15 feet high and about 10 feet wide, ei^ch of the outer pas- 

 sage-ways being 11 feet in width by 15 feet at the highest point. 

 The width of the river at Washington Street is about 180 feet, 

 while the whole length of the tunnel, after providing for a suita- 

 ble inclined plane at each entrance, will be about 9-45 feet. The 

 floor of the tunnel at the centre of the river will be about 32 feet 

 below low-water mark. 



The tunnel is to be constructed by means of coifer-dams, which 

 are to be placed, with their pi'otections, up and down the river, 

 within a space, north and south, of not over 150 feet, and, east 

 and west, of not over 100 feet, so as to have a space of nearly 50 

 feet for the passage of vessels entirely unobstructed. Ui^on the 

 completion of the work, such portions of the dams as may remain 

 will be entirely removed, so as to leave the river as unoljstructed 

 as at present. The tunnel proper is to be formed of the most 

 perfect brick and stone masonry, backed with concrete, wliile the 

 floor of roadways will be neatly paved with Nicholson pavement. 

 The work is to be completed in March, 1868. 



Should this latter work prove a success, we may look for the 

 general adoption of the tunnel instead of the bridge i)lan at all 

 our river crossings ; and, as a consequence, the absolute freedom 



