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 It has been replaced by the electric traction elevator.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. [Illustration: AN ELEVATOR OF THE MIDDLE AGES History tells us this form of elevator was used in monasteries for hoisting passengers and supplies.] [Illustration: ELEVATOR INSTALLATION IN THE WOOLWORTH BUILDING, NEW YORK] To obviate danger from accidents, safety devices are installed for gripping the rails in case of the car attaining excessive speed. Another feature of security is the oil cushion buffer. One of these is placed in the hoistway under the car and one under the counterweight, they being capable of bringing a car to rest from full speed without discomfort to those in the car. The oil in the buffer is driven by the impact of the car from one chamber of the buffer to another, but this is made to take place at a fixed rate of retardation, the oil acting as a liquid cushion which stops the car gradually and without shock. To do business in the modern lofty building without the aid of elevators (or lifts, as they are called in England) is today out of the question, while the great grain-transporting edifices in cities in which our annual crops are lifted and lowered, are known by the specific name of elevators. There is, however, another means of getting up and down stairs which is coming somewhat rapidly into use and in which the old stairway is restored. It is one in which the stair itself does the moving instead of the passengers upon it. This new and interesting device is known as an escalator. [Illustration: A STEAM-DRIVEN ELEVATOR OF EARLY DATE] The Escalator. The earliest way to get upward from the ground was that adopted by climbing animals in clambering up tree trunks, and by man himself in “shinning” up trees by aid of his arms and legs. This was followed by the plank leading from a lower to a higher level, by the ladder, and finally by the stairway. In our days the stairway has been put on a set of revolving wheels and moves upward itself, carrying its passengers with no need on their part to use their feet. This simple but effective device is known as the escalator.