With Lagrange and Gauss the nineteenth century rigorization of analysis got under way. Later nineteen-century matbematicians who played outstanding roles in this work were the Frenchman,Augus in-Louis Cauchy (1789-1857), and the German, Karl Weierstrass (1815-1897) As noted above,our present definitions of limit,continuity, the derivative as the limit of difference quotient, and the definite integral as the limit of a sum are substantially those given by Cauchy. Cauchy wrote extensively and profoundly in both pure and applied mathematics, and he can probably be ranked next to Euler in volume of output, His numerous contributions to advanced mathematics include researches in convergence and divergence of infinite series, real and complex function theory, differential equations, determinants, probability, and manthematical physics. His name is met by the student of calculus in the so-called Cauchy root test and Cauchy ralio test for con vergnce or divergence of a series of positive terms, and in the Cauchy product of two given series. In even a first course in complex function theory one encounters. The Cauchy inequality, Cauchy”8 integral formula, Cauchy” s integral theorem, and the basic Cauchy-Riemann differential equations.