. The street railway review . NGITUDINAL SECTION OF TUNNEL. at two places in a long block, is placed a call box, towhich every gripman has a key. In event of trouble,strand or blockade, an alarm is turned in. One turnrings the gong once and calls for the stopping of thecable, three rings summon the wrecking wagon andtwo rings means start the rope. At the same time arelay telegraph device prints on a paper ribbon the num-ber of the block. There are 61 boxes on the line, 31 onBlue Island avenue and 30 on Halsted street. consists of one elliptical span of 30 feet. The length ofthe tunnel proper,
. The street railway review . NGITUDINAL SECTION OF TUNNEL. at two places in a long block, is placed a call box, towhich every gripman has a key. In event of trouble,strand or blockade, an alarm is turned in. One turnrings the gong once and calls for the stopping of thecable, three rings summon the wrecking wagon andtwo rings means start the rope. At the same time arelay telegraph device prints on a paper ribbon the num-ber of the block. There are 61 boxes on the line, 31 onBlue Island avenue and 30 on Halsted street. consists of one elliptical span of 30 feet. The length ofthe tunnel proper, from portal to portal is 920 feet. Theeast approach is 278 feet and the west approach is 316feet. The gradients run as shown in the diagram. During the progress of construction, the buildings toovaluable to be destroyed, but whose foundations had tobe undermined, were elevated on hundreds of hydraulicjacks each capable of lifting 30 tons. In no case wasa wheel disturbed of the manufacturing interests in the 288 ^f\fwdrj{aAyw^. INTERIOR OF TUNNEL DURING CONSTRUCTION, SHOWING METHOD OF BRACING. building nor an elevator stopped. The network of rail-road tracks was passed in safety as well as the docks andthe river. The shifting claj which has marvellous powerof torsion was successfully restrained until the brick waslaid. Three million bricks were used in the work, 6,000barrels of hydraulic and 15,000 barrels of Portlandcement. The tunnel is of brick in seven rings, aggregat-ing 32 inches thick, and the portals of Bedford two tracks for the cable are spaced about 15 feetfrom center to center, thus giving safe clearance alongthe walls and between cars. The sumps and drains for seepage and storm waterare amply sufficient and the tunnel will be dry but inter-esting even in wet weather. The tunnel is 15 feet 9inches high at the center. The river section is concreted,covered with asphalt mortar and laid with flagging, sothat by no mischance can the tunnel be broken into by ave
Size: 1832px × 1364px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1800, bookdecade1890, booksubjectstreetrailroads
