The author [image]A discusses the integral P(t)[long dash]\ B(t[long dash]x)l(x)dx, where J o P(t) stands for the population at time t, l(x) is the chance at birth of attaining age x and A is the upper limit of age at death. The function l(x) is replaced by the function,[image] - [* s(xJt)=:e Jo [image] x + y y, which takes into consideration changing mortality. Most of the paper is devoted to finding [mu](y t)=Q(y) [center dot] R(y[long dash]t), where Q(y) is a function of age and R(y[long dash]t) is the generation function involving the difference between the age y at the time t. The ratio R(y[long dash]t[image])/R(y[long dash]t) is found by fitting a logistic curve to mortality rates of English [male][male] from 1941 to 1930; Q(y) . R(30) is found by fitting a Makeham curve to these data for various values of y. From this information the function s(x,t) is found and used to express the value of P(t).