Blaise Pascal, French mathematician, physicist and philosopher, c 1650.
© Science Museum / Science & Society Picture Library
Portrait made in 1763, of Pascal (1623-1662) who is credited with founding the modern theory of probability. He also discovered the properties of the cycloid (or roulette), contributed to the advance of differential calculus and in 1647 invented the first calculating machine. As a physicist, his attempts to discredit the notion that 'nature abhors a vacuum' led to the invention of the barometer, hydraulic pres and syringe. The SI unit (International System of units) of presure, the Pascal, and a computer programming language are named after him. Illustration from 'Histoire des philosophes modernes' (History of modern philosophers), by Alexandre Saverien (1720-1805), published in Paris in 1763.