Observations on reversionary payments [microform] : on schemes for providing annuities for widows, and for persons in old age, on the method of calculating the values of assurances on lives, and on the national debt : also, essays on different subjects in the doctrine of life-annuities and political arithmetic, a collection of new tables, and a postscript on the population of the kingdom / by Richard Price / the whole new arranged and enlarged by the addition of algebraical and other notes, and the solutions of several new problems in the doctrine of annuities / by William Morgan