Today is 11th March, 2010. 1. On today in 1822, a mathematician Joseph Bertrand was born. He was famous for his work on differential geometry and probability theory. For example, he discovered a paradox on continuous probabilities, known as Bertrand's paradox. Besides, an important theorem on the distribution of primes, named as Bertrand's Postulate, was first proposed by him . However, he could not prove it. It remained unsolved until Chebyshev's work in 1850.