of Tarentum, a disciple of Pythagoras, about 516 B. C. It does not appear to have been used by the ancient Egyptians.
The combination of pulleys is ascribed to Archimedes, who died 212 B. C.
Vitruvius described the pulley.
He refers to the sheaves (orbicuti) in the blocks (trochlea), and defines the system by the aggregate number of sheaves in the two blocks, — trispastos, pentaspastos, etc.
We read of pulleys on the great ship built by Archimedes for Dionysius of Syracuse, about 250 B. C. They were used for hoisting stones into the towers for the supply of the catapults and other engines.
The cord and pulley principle is employed in the tendons of animals, some of which have their directions changed by passing over fixed pulleys of cartilage.
One of the muscles by which the eyeball is moved is called the trochlearis, from the trochlea or pulley through which the tendon passes.
The pulley is classed as one of the mechanical powers.
Pulleys without blocks or carri