CABLE-RAILWAYS. 



123 



strain far greater than the engineers had an- 

 ticipated for the trial-trip. With one trifling 

 check, however, the perilous ascent was ac- 

 complished, the crowd racing alongside the car 

 and fighting recklessly for places to hold on by. 

 A month later the cars began to run regularly, 

 and, save for the changes and alterations in- 

 separable from new inventions, the road has 

 been successfully operated ever since. A three 

 years' trial so thoroughly demonstrated the 

 usefulness of the system that other roads were 

 built in San Francisco some of them distinct 

 infringements upon Mr. Hallidie's patents, and 

 so adjudged by the courts and at present there 

 are more than fifty miles of street-railway in 

 that city alone constructed practically on the 

 same plan. Although designed at first only to 

 overcome excessive gradients, it was found in 

 practice that the system was more economical 

 than horse-traction, even on level ground, and 

 it is now extensively adopted in New York, 

 Chicago, Philadelphia, and other large cities of 

 the United States, and even in New Zealand. 

 That it will speedily be introduced in all civil- 

 ized lands can hardly be doubted. 



The most approved construction of a cable- 

 road for street-service calls firstly for a tunnel 

 under the railway, in which an endless wire 

 rope may run, resting upon a succession of fixed 

 wheels or sheaves. The difficulties in the proper 

 construction of such a tunnel are many, and it 

 has only been by successive improvements that 

 approximate perfection has been reached. The 

 necessity of having an open, longitudinal slot 

 in the top of the tunnel weakens the structure 

 where it should be strongest, and renders it 

 impossible to employ the ordinary cross-ties 

 used in railway construction. The absence of 

 these ties favors the tendency of the rails to 

 spread apart, and the tendency of the grip-slot 

 to close, and this is largely increased by the 

 ceaseless jarring of the ordinary business traf- 

 fic of the street. It was found impracticable 

 to make any system of half-ties sufficiently 

 rigid. Accordingly, the latest tunnels are so 

 constructed that, if the whole street outside 

 of the rails were washed away, the road-bed 

 would remain intact, resting upon independent 

 piers of masonry. To effect this, V-shaped 

 yokes or ribs of iron are bent or cast in the re- 

 quired shape. The rails are bolted to the tops 

 of the arms of the yoke, and the whole struct- 

 ure stiffened with cross-braces, resting upon 

 solid piers, with foundations as deep as the 

 nature of the soil requires. Within the arms 

 of the yoke is the hollow iron tube, or tunnel, 

 with its longitudinal slot, through which con- 

 nection is made between car and cable. (See 

 Fig. 3.) When all the parts are in place a 

 mold is made, inclosing the whole framework, 

 and the open spaces (excepting, of course, the 

 tunnel) are filled with hydraulic cement. It 

 will be noted that the carrying-sheave is not 

 centered under the slot, as in Fig. 1. This is 

 done to avoid the drip of water and dirt from 

 the opening, which might injure the cables. 



The existing system is made possible by the 

 improved method of manufacturing wire rope, 

 which is now made of crucible steel wire, 

 capable of bearing a tensile strain of 120 tons 

 to a square inch of sectional area. The light- 

 ness, strength, and comparative cheapness of 



FIG. 3. RECENT CONSTRUCTION. 



the cable is an important element in the first 

 cost. The maximum all-round length of an 

 endless cable varies with the local conditions. 

 The main line on Market Street, San Fran- 

 cisco, is 24,125 feet long, and works satis- 

 factorily, but the line is straight and the 

 grades moderate. The Clay Street line, in 

 the same city, runs up and down grades vary- 

 ing from 1 in 28 to 1 in 6, reaching a height 

 of 307 feet at a distance of 2,800 feet from the 

 starting-point. The total length of the cable 

 is about 7,000 feet. Provided the line is per- 

 fectly straight, and moderately level, it is evi- 

 dent that the cable will be held in place by its 

 own weight, and will run upon the grooved 

 carrying-sheaves ; around a large wheel of at 

 least 100 times its own diameter, at the end of 

 the line, and back to the starting-point, without 

 anything to hold it in position so long as it is 

 kept taut. If it is to draw a heavy load, it 

 must also be prevented from slipping. The 

 device for keeping the rope taut is identical in 

 principle with that of Chapman's patent (Fig. 

 1). Slipping is prevented either by taking 

 several turns around a drum, or a half-turn 

 around a grooved wheel, provided with auto- 

 matic clasping-jaws, or as shown in Fig. 4, 

 which is one of the most approved modern 

 methods : A is the incoming and B the out- 

 going cable, C and C' are the friction-pulleys, 

 I) is the tension-pulley, and E the weight that 

 pulls it away from C and C', and keeps the 

 cable taut. The incoming cable just clears the 

 top of C', passes three fourths round C', three 

 fourths round C, below C', and thence round 

 D, where it becomes the outgoing cable. The 

 arrows show the direction of movement. The 

 tension-pulley D is mounted on a carriage, not 

 shown in the diagram, and the weight E is 



