Throughout this century mortality has been declining and if an exponential curve in the Gompertz form μx = bcx is fitted to recent English Life Tables b has been decreasing as we would expect. Between the 1911 Table and the 1951 Table, 105b has fallen from 18 to 6 for males and from 9 to 2 for females. But c has been increasing—from 1·087 to 1·103 for males, and from 1·094 to 1·112 for females. What feature of mortality can it be that has been deteriorating in this scientific age? Has c any counterpart in reality? Or is it just a mathematical by-product of our system of description?