224 MilLOSOPHlCAL TRANSACTIONS. [aNNO 1751. 



that of giving a greater degree of certainty to the calculations of the values of 

 annuities on lives ; a benefit too considerable to be passed by silently. The pre- 

 sent possessors of entailed estates are, in common law, justly called tenants for 

 life. Marriage-settlements generally convey the reversion of a considerable part 

 of the bridegroom's estate to the bride, for her natural life after his decease ; to 

 which two things all the freehold estates in these kingdoms are liable : and if to 

 these be added the great number of copyholds determinable on lives ; the great 

 quantities of church, college, and other lands, leased on lives, and the estates 

 possessed by ecclesiastical persons of all degrees ; we shall find that the values of 

 the possessions and reversions, of much the greatest part of the real estates in 

 these kingdoms, will one way or other depend on the value of lives. Likewise 

 the incomes annexed to all places, civil and military, all pensions, and most cha- 

 ritable donations, are annuities for life. The interest or dividends of many per- 

 sonalities in the stocks have been, by the wills of their possessors, rendered of 

 the same kind ; besides which, there are some annuities on lives which have 

 been granted by the government, and have parliamentary security for their pay- 

 ment ; and others that have been granted by parishes, in consequence of acts of 

 parliament made for that purpose. 



After this summary view of the extensive property, vested in annuities on lives, 

 it would be very easy to name a great variety of circumstances, in which the 

 computations of the values of 1, 2, or more lives, will become necessary to 

 those persons who do not chuse to have their property determined by customs 

 which seem to have been established merely for want of good methods of calcu- 

 lation. 



The advantages attending the determination of those things by calculation, 

 rather than by custom, being therefore considered as evident, it may seem 

 strange that, notwithstanding many of these tenures have subsisted from the very 

 origin of private property in these kingdoms, yet we do not meet with so much 

 as an attempt towards computing their values, till that of the late justly cele- 

 brated Dr. Halley, by the assistance of the bills of mortality of Breslaw in Silesia, 

 which was soon followed by Mr. De Moivre's truly admirable hypothesis, that 

 the decrements of life may be esteemed nearly equal, after a certain age. It has 

 been the opinion of some authors, that, since his hypothesis was originally de- 

 rived from the Breslaw observations, it cannot be near so well adapted to the in- 

 habitants of these kingdoms, as what has been derived from the bills of morta- 

 lity of London. But this argument does not, Mr. D. conceives, appear to be 

 conclusive; 1st, because those bills, as hitherto kept, are not well adapted to 

 answer this purpose ; 2dly, because the manner in which the inhabitants of Lon- 

 don, and those of most of the country towns and villages, live, their occupations, 

 diet, and diversions, nay the very air they breathe, are as different, as those of 



