Observations on reversionary payments [electronic resource] : 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. To which are added, four essays On different Subjects in the Doctrine of Life-Annuities and Political Arithmetick. Also, an appendix and supplement, Containing additional Observations, and a complete Set of Tables; particularly, several new Tables of the Probabilities of Life in different Situations, and of the Values of Annuities on Lives. The third edition, much enlarged. By Richard Price, D. D. F. R. S.