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 : 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, the solutions of several new problems in the doctrine of annuities, and a general introduction, by William Morgan