92 TUN.NKLIM; 



were stretched longitudinally between the beams forming the 

 polygons ,of the consecutive timber structures. 



Masonry. After the upper portion of the tunnel section 

 had been excavated, the arch was built with its feet resting 

 upon heavy planks. For the construction of the arch light 

 centers were used. The arch was made of brick, and rested on 

 the unexcavated portions of the bench. When these were 

 removed, pillars of rock from 6 to 8 ft. long were left at equal 

 intervals between them. In the spaces left vacant, balks of 

 timber were inserted in order to support the arch. In the 

 space between the rock pillars the side walls were built up 

 from foundation and the arch underpinned ; then the rock pillars 

 were in their turn battered down, new timbers were inserted 

 to support the arch, and the side walls were built and the arch 

 underpinned. In this way the masonry of the lining was made 

 continuous. At every 3,000 ft. large niches were built, while 

 all along the line on both sides small sheltering niches Trere 

 built 150 ft. apart 



Hauling. In the Mont Cenis tunnel all the hauling was 

 done by horses. On the floor of the drift small tracks were 

 placed, upon which ran the cars that removed the broken rock 

 produced by blasting at the front. At the end of the drift the 

 small cars dumped the rock into larger cars running on the 

 floor of the part No. 2 which was the tunnel floor. There a 

 single track was laid, which was afterward switched into a 

 double track where the full section of the tunnel was opened. 

 The materials excavated from the upper portion of the profile, 

 by means of openings left in the roof of the drift, were loaded 

 directly on to the large cars running on the tunnel floor. 



Ventilation. Ventilation was at first obtained by the air 

 discharged from the drills, which exhausted from 250,000 to 

 280,000 cu. ft. of fresh air every hour at the front. When this 

 quantity was considered too small, a blower 2.5 ft. in diameter 

 was employed. It w r as operated by a small compressed air 

 motor, and the air w r as driven to the front through a 10 in. box 



