CHEBICHEV, PAFNUTIY LVOVICH after N. I. Lobachevskiy, the most distinguished of Russian mathematicians, was born at Borovsk on May 26, 1821. Educated at the University of Moscow in 1859, he became professor of mathematics in the University of St. Petersburg, a position from which he retired in 1880. He became a correspondent in 186o, and in 1874 associe etranger of the Institute of France. He was also a foreign member of the Royal Society of London. In 1841 he published a valuable paper, "Sur la convergence de la serie de Taylor," in Crelle's Journal. He wrote much on prime numbers; in one paper ("Sur les nombres premiers," 1850) he established the existence of limits within which must be comprised the sum of the logarithms of the primes inferior to a given number. He devoted much attention to the problem of obtaining rectilinear motion by linkage. The "Chebichev's parallel motion" is a three bar linkage, which gives a very close approximation to exact rectilinear motion, but he failed to devise one producing true rectilinear motion. Such a linkage was discovered by one of his pupils, Lipkin, who, however, had been anticipated by A. Peau cellier. His mathematical writings cover a wide range of subjects, such as the theory of probabilities, quadratic forms, theory of integrals, gearings, the construction of geographical maps, etc. He also published a Traite de la theorie des nombres. He died at St. Petersburg on Dec. 8,