Now we discuss the work of Isaac Barrow (1630--1677) on the FT of C. It was well--known by 1650 that the area under the graph of y=xn is 1/(n+1) xn+1, when n is a rational not -1 and that the derivative of 1/(n+1)xn+1 is xn, so both parts are valid for this case. But there was no general Theorem published before Barrow and for this reason, some scholars regard him as the Father of Calculus.