An essay to ascertain the value of leases and annuities for years and lives, and to estimate the chances of the duration of lives. Wherein are many observations on bills of mortality, on the State of the Coin, the Interest of Money, and the Price of Things, in different Ages: And Notice taken of several Writers on this Subject. Also Rules are therein given-for reducing Leases for Years or Lives to clear Annuities; shewing what Deductions are necessary to be made for that Purpose, out of the improv'd Rents on such Estates; without which the Value of them cannot be rightly ascertain'd; and stating at what Rate Interest ought to be computed in purchasing Annuities or Leases, either for Years or Lives, if the Purchasers expect to have the Principal reimbursed, or an Equivalent. A Method likewise is shewn, of calculating to what Number of Years any given Life or Lives, on an even Chance, may probably extend, whereby Estates held by those Tenures are converted into Terms certain, and the Value of them thereby readily seen: And all other Schemes for adjusting such Value are shewn to be false or precarious. To which are added, in the Appendix, Tables adapted to these several Purposes, and to most Cases which may arise on the Value of Estates of this Kind. By Weyman Lee, Esq