ON LIFE CONTINGENCIES. l6l 



false. For it is a law, were it the only one, that no 

 individual shall attain the age of 200 years. So much 

 is known to all ; but to those who consider the subject 

 more closely, by the aid of recorded facts, it may be 

 made as evident as the existence of a limit to human life, 

 that the casualties of mortality are distributed among 

 mankind in so uniform a manner, that the average 

 existence of a thousand infants will differ very little 

 from that of another thousand born in the same country 

 and station of life. It is true that differences of race, 

 climate, manner of living, &c., &c., produce marked 

 effects upon the duration of life; which is no more 

 than might be expected : but it is equally true that the 

 notorious individual uncertainty of life cannot be dis- 

 covered in the results of observations made upon masses 

 of individuals. 



There are various results of observation, which are 

 called tables of mortality, which differ only in the 

 methods of presenting the same sets of facts. Firstly, 

 we have what may be called tables of the numbers living. 

 These show, for a given number born, how many attain 

 each year of age. Thus, in the Carlisle table, opposite 

 to and 50, we find 10,000 and 4*397, indicating that, 

 according to observations made at Carlisle, the propor- 

 tion of those born to those who saw their fiftieth birth- 

 day, was that of 10,000 to 4397. Again, opposite to 

 60, we find 3643, meaning, that of 4397 persons aged 

 50, 3643 attain the age of 60. Secondly, we have tables 

 of yearly decrements, in which the same number of per- 

 sons are supposed to be alive at every age, and the pro- 

 portion who die in the next year is set down in the table. 

 Thus in the government annuity tables, opposite to 50 

 and 60, we find l6l and 315, meaning that, according 

 to the observations from which these tables were con- 

 structed, of 10,000 persons aged 50, l6l died before 

 completing the next year of life ; and of 10,000 persons 

 aged 60, 315 died before attaining the age of 6l. 

 Thirdly, we have tables of mean duration of life (com- 

 monly called expectation of life), which show the average 

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