664 KANSAS CITY REVIEW OF SCIENCE. 



poses. In this way longer holes can be cut, and heavier charges of dynamite em 

 ployed. 



The first sub-aqueous tunnel in England was that under the Thames from 

 Wapping to^Rotherhithe, known as the Thames Tunnel. It was begun in 1807 ; 

 the operations were stopped after a time ; but recommenced by Sir M. I. Brunei, 

 in 1825. The work was again interrupted by accidents ; but the causeway was 

 eventually opened for foot-passengers in 1843. In the year 1867 it was purchased 

 by the East London Railway Company. It is 1,200 feet in length. Another 

 subway is planned between the north side of the Thames and South Woolwich ; 

 it will be much deeper below the bed of the Thames than the older subway, and 

 is to be constructed to admit of the transit of troops and war-material from Wool- 

 wich to the north side of the river, thus avoiding the circuitous route over London 

 Bridge. Of this class we must also mention the Severn Tunnel, commenced in 

 1875, and now well on toward completion; but the bursting of a spring last year 

 caused a serious interruption to the operations. The cutting has been mostly 

 through rock, and about 100 yards in the centre of the channel yet remains un- 

 pierced. 



Among other important works, the soft of the eminent engineer above men- 

 tioned constructed Box Tunnel, on the Great Western Railway, in the vicinity 

 of Bath ; it is nearly four miles long. The Woodhead Tunnel, near Manchester, 

 is three miles in length; a second cutting, of the same dimensions, was afterward 

 made parallel with it, but separated by a longitudinal pier. The Kilsby Tunnel, 

 on the London and Northwestern Railway, was four years in construction ; it is 

 2,400 yards long, and cost ^^350, 000; nearly four times the original estimate. 

 Pecuhar difficulties were encountered in making the Sydenham Tunnel (London, 

 Chatham and Dover Railway). It is cut through the London clay, and while 

 the works were in progress the clay commenced swelUng and crushing the mason- 

 ry. This was so serious that over 8,000 cubic yards of work had to be rebuilt. 



Considerable progress is now being made with borings for the tunnel to be 

 cut by the Mersey Railway Company under the bed of the Mersey. The shaft 

 on the Birkenhead side has been sunk to a depth of about 120 feet with most 

 satisfactory results. The boring is through the New Red Sandstone; on the 

 Liverpool side, a depth of 100 feet has been reached. It is scarcely necessary to 

 mention the tunnel which forms the chief feature of the Metropolitan (or .Under- 

 ground) Railway of London, opened January 10, 1863, and since extended in 

 several directions. A similar work is projected for Paris, at an estimated cost of 

 ;^6, 000,000. There are now over eighty miles of tunneUng in England. 



Tunnels for portions of canal in hilly regions are sometimes of great length — 

 such as the Can"al de St. Quentin, more than seven miles long; the Huddersfield, 

 and the Mauvages (Canal du Marne au Rhin), three miles each; Sapperton, 

 Thames and Medway, Dudley, Blisworth, Soussey, Pouilly, ranging from two to 

 four miles. 



Transatlaiitic enterprise of this class has made great advances of late years. 

 We select two or three out of nearly a score which deserve mention. The Hoosac 



