+---------------+------------+---------+--------+------------+ |NAME OF TUNNEL.| DIMENSIONS | DEPTH |PROGRESS|CHARACTER OF| | | IN FEET. |IN FEET. |IN FEET.| MATERIAL. | +---------------+------------+---------+--------+------------+ |Hoosac: | | | | | | East shaft |15.4  × 27.7| 1035 | 21.7 |Mica schist.| | West shaft | 8  × 16 | 267 | 16.7 |Gneiss. | |Musconetcong: | | | | | | Vertical shaft| 8.35 × 16.7| 113.5 | 100 |Loose rock. | | Inclined shaft| 8.35 × 26 | 304. | 32 |Loose rock. | +---------------+------------+---------+--------+------------+ The average monthly progress of sinking shafts in treacherous soils may be assumed to be as follows: clay of first variety, 50 ft. to 75 ft; clay of second variety, 36.75 to 50 ft; clay of third variety, 23.4 ft. to 36.75 ft; quicksand, 16.7 ft. to 33.4 ft. For the reason that the details change with the various conditions encountered in every work, all the tunnel operations have been treated in a general way, purposely avoiding to give any detail. Also the rate of progress and items of cost of tunnels have been given in a broad manner because they greatly vary in the different works. This information, however, can be easily obtained by consulting the Engineering Magazines, where are reported all the tunnel works of America and Europe, and where are given so many details which are very valuable to expert engineers in charge of similar works, but not to students and people who are looking only for general knowledge. INDEX Accidents and Repairs in the Belgian Method, 152 Accidents in Tunnels: After Construction, 308 Baltimore Belt Line, 165 Chattanooga Tunnel, 311 During Construction, 301 General Discussion, 301 Giovi Tunnel, 309 Repairing of, 304 Acetylene Gas Lighting, 334 Air Compressors, Description of, 87 Air Locks, 264-272 Air Pressure, 268 American Method: General Description, 172 Excavation, 172 Strutting, 174 Hauling, 175 Arrangement of Drill Holes, 90 Artificial Ventilation, 327 Austrian Method of Tunneling: Advantages and Disadvantages, 180 Excavation, 176 General Description, 176 Lining, 180 Strutting, 177 Average Progress in Tunnels, 342 Baltimore Belt Line Tunnel, General Description, 160 Barlow’s Shield, 242 Beach’s Shield, 246 Belgian Method: Accidents and Repairs, 152 Advantages and Disadvantages, 152 Excavation, 145 General Description, 144 Lining, 148 Hauling, 150 Strutting, 146 Bench, 131 Bends, 268 Blackwall’s Tunnel Shield, 248 Blasting-cone, 33 Blickford Match, 31 Boston Subway: General Descriptions, 203 Roof Shield, 251 Boulder Tunnel Relined, 315 Box-cars, 61 Box Strutting, 51 Brandt Drilling Machine, 28, 112 Brown, W. L., 269 Brunel’s Shield, 240