INTRODUCTION 



tunnel was 510 ft. long, 22 ft. wide, and 29 ft. high, and was 

 excavated through tufa. It was left unlined for seven years, 

 and then was lined with masonry. 



With the advent of gunpowder and eanal building the first 

 strong impetus was given to tunnel building, in its modern 

 ', as a commercial and public utilitarian construction, since 

 the days of the Roman Fmpire. Canal tunnels of notable 

 size were excavated in France and Kngland during the last 

 half of the 17th century. These were all rock or hard-ground 

 tunnels. Indeed, previous to 1800 the softground tunnel was 

 beyond the courage of engineer except in sections of such 

 small size that the work better deserves to be called a drift or 

 heading than a tunnel. In 1803, however, a tunnel 24 ft. 

 wide was excavated through soft soil for the St. Quentin Canal 

 in France. Timbering or strutting was employed to support 

 the walls and roof of the excavation as fast as the earth was 

 removed, and the masonry lining was built closely following it. 

 From the experience gained in this tunnel were developed the 

 various systems of soft-ground suhterrannean tunneling since 

 employed. 



It was by the development of the steam mil way, however. 

 that the art of tunneling was to l>e brought into its present 

 prominence. In 1820-26 two tunnels were built on the Liver- 

 pool A: Manchester Ry. in Fngland. Tin's was the l>eginning 

 of the rapid development which has made the tunnel one of 

 the most familiar of engineering structures. The first railway 

 tunnel in the United States -WHS built on the Alleghnny & 

 1'ortage U.K. in Pennsylvania in 1831-33; and the first canal 

 tunnel had been completed about 18 years previously (1818-21 ) 

 by the Schuylkill Navigation Co., near Auburn, Pa. It would 

 be interesting and instructive in many respects to follow the 

 rise and progress of tunnel construction in detail since the con- 

 struction of these earlier examples, but all that may be said 

 here is that it was identical with that of the railway. 



The art of tunneling entered its last and greatest phase 



