[Illustration: IN ORDER TO ASCEND MORE EASILY, MAN DEVISED THE STAIRWAY, FROM WHICH, IN TURN, WAS DEVELOPED THE ESCALATOR, IN ORDER TO FURTHER ELIMINATE PHYSICAL EFFORT]
[Illustration: PRIMITIVE MAN PULLED HIMSELF UP A LADDER WHEN HE WANTED TO GO FROM ONE LEVEL TO ANOTHER]
The elevator is not exactly a new idea. Its pioneer form may be traced back to the Middle Ages, when heavy weights were lifted by aid of an apparatus worked by hand power. But it was not until well on into the nineteenth century that the steam-power elevator came into service. The first example is said to have been produced by Elisha Graves Otis, who applied steam power to an elevating machine in a little shop at Yonkers, on the banks of the Hudson, New York. A few years later, at the International Exhibition of 1853 in New York, he displayed the first elevator with a safety device to prevent the car from falling in case of a broken cable.
The elevator was then a novelty. It has long since grown into a necessity. It is to be seen in all hotels and high buildings, and the art of getting up stairs has in very many cases changed into that of being lifted up by a moving car in an enclosed shaft or cage. The steam elevator, at first used, has now in great measure been replaced by the electric elevator, the first moved by an electric motor being the Otis elevator installed in the Demarest Building, New York, in 1889. This is still in active use.
The first electric elevators were confined to the drum type of machine, these having a grooved drum around which the hoisting cables were wound, the drum being revolved through worm gearing by an electric motor. But the erection of buildings, ranging from 200 to 700 feet in height has put this type of traction out of business on account of the great size of drums required and the necessary slowness of motion. It has been replaced by the electric traction elevator. In this the hoisting cables from which the car is suspended have at the other end a counterweight and pass around driving sheaves in place of a drum. This, in its latest form known as the gearless traction elevator, does away with all intricate machinery, and yields a machine moving with equal speed whatever the height.
