An essay to ascertain the value of leases and annuities [electronic resource] : 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; and their Rules and Tables, particularly for the Valuation of Annuities for one or more Lives, are demonstrated to be erroneous.