The operation may be illustrated by that of an ordinary hoisting-tackle in which a heavy load is raised a short distance by hauling in a com paratively long length of hoisting-rope with a pulling force inuell snmller than the weight of the load lifted. By a reverse of this operation a heavy load moving a short distance will hoist a light load through a long distance. This is exactly the operation performed by the arrange ment of fixed and traveling sheaves of a hydraulic elevator plant. The operation of the most recent.
type of electric elevator is much similar to that just described for hydraulic elevators. As ap plied to the elevators of the thirty-story fins Syndicate Building. in New York City, the elec tric-elevator mechanism was as shown in the companying diagraun. Here it will be observed that a nut traveling on a screw operated by an tric motor gives the er motion to the ing sheaves. In many forms of electric elevator the motor operates a drum on which the ing-rope is wound and wound to hoist and lower the car. if in this struction we substitute for the electric motor a steam-engine to operate the drum, we have the ordinary steam - elevator arrangement. The only other form of hydraulic elevator than those scribed has a vertical cylinder sunk in the ground with the rod extending upward and the ear supported rectly on the piston-rod. This form of elevator is most suitable for short lifts, and is generally only used for freight vators.
As indicating the na ture and size of sonic of the elevator installations in tall buildings, the fol lowing figures are of in terest: \lonadnock Block, Chicago, 16 hy draulic elevators. all of IC-stories travel ; Saint
Paul Building. New York, ti hydraulic ele vators, two 26-stories travel, two 16-stories travel, and two 9-stories travel; Bowling Green Buildings, New York. nine hydraulic elevators, 16-sto•ies travel; vins Syndieate Building, New York, 15 electrie elevators, live 25-stories travel. five 26 stories travel. one freight elevator 26-stories travel, two tower elevators. Iwo sidewalk elevators. The Saint Paul Building plant is a good example of express elevator service. Two elevators in this building travel to the ninth floor, stopping at every door; two travel to the sixteenth floor. passing every 11001' below the ninth without stops, or 'express,' and stopping at every door from the ninth to the sixteenth, or two travel to the twenty fifth floor, running express to the sixteenth door and local above the sixteenth door. Among ele vators designed to carry heavy loads may be mentioned those at the Weehawken. N. J., ter minus of the North Iludson County Railway, which have a lift of 14S feet. with ears holding 14(1 persons each. The elevator in the Wash ington Monument, Washington. I). C., has a travel of 500 feet. and those of the Eiffel Tower (q.v.) have a travel of 450 feet. For grain elevators, see that title, and for elevators or hoists for tunneling and mining work, see TUN NELS and AIINING.