To these curves, which were also applied to effect some quadratures, Evangelista **Torricelli** gave the name of "Robervallian lines."

Benedetto Castelli (1577-1644), and Evangelista **Torricelli** (1608-1647), two of the disciples of Galileo, applied the discoveries of their master to the science of hydrodynamics.

The theorem of **Torricelli** was employed by many succeeding writers, but particularly by Edme Mariotte (1620-1684), whose Traite du mouvement des eaux, published after his death in the year 1686, is founded on a great variety of well-conducted experiments on the motion of fluids, performed at Versailles and Chantilly.

Incited by the discoveries of Galileo, Pascal and **Torricelli**, he attempted the, creation of a vacuum.

The cycloid was a famous curve in those days; it had been discussed by Galileo, Descartes, Fermat, Roberval and **Torricelli**, who had in turn exhausted their skill upon it.

Evangelista **Torricelli**, in the first regular dissertation on the cycloid (De dimensione cycloidis, an appendix to his De dimensione parabolae, 1644), states that his friend and tutor Galileo discovered the curve about 1599.

**Torricelli**, by employing the "method of indivisibles," deduced that the area was exactly three times that of the generating circle; this result had been previously established in 1640 in France by G.

The trochoids were studied by **Torricelli** and F.

EVANGELISTA **TORRICELLI** (1608-1647), Italian physicist and mathematician, was born at Faenza on the 15th of October 1608.

Its communication by Castelli to Galileo in 1641, with a proposal that **Torricelli** should reside with him, led to **Torricelli** repairing to Florence, where he met Galileo, and acted as his amanuensis during the three remaining months of his life.

After Galileo's death **Torricelli** was nominated grand-ducal mathematician and professor of mathematics in the Florentine academy.

345; Ghinassi, Lettere fin qui inedite di Evangelista **Torricelli** (Faenza, 1864); Tiraboschi, Storia della lett.

He continued his scientific correspondence with unbroken interest and undiminished logical acumen.