LIFE. 



The probability that a life of any pre- 

 sent age shall continue a certain number 

 of years, or shall attain to any other given 

 age, is the fraction whose numerator is the 

 number of the living in the table opposite 

 to the given age, and the denominator the 

 number opposite to the present age of 

 the given life. Thus the probability that 

 :i life of 25 shall attain to the age of 45, 



3248 

 or live 20 years, is , ... The difference 



47oJ 



between this fraction and unity gives the 

 probability that the event will not happen; 

 the probability that a life of 25 will not 



live 20 years, is therefore - , conse- 

 quently the odds of living to dying in this 

 period are more than 2 to 1. The pro- 

 bability that a person of 32 years of age 

 .shall attain to 59 years, appears by the ta- 

 ble to be ~. or nearly an even chance. 



In order to find the expectation of 

 life at any age, from a table, like the 

 above, which shows the number that die 

 annually at all ages, divide the sum of 

 all the living in the table, at the age 

 whose expectation is required and at 

 all greater ages, by the sum of all that 

 die annually at that age and above it ; 

 or, which is the same, by the number 

 of the living at that age ; and half unity 

 subtracted from the quotient will give 

 the expectation required. Thus, at the 

 age of 65, the sum of all the living at 

 that and all greater ages, is 18,580 ; 

 the number living at that age is 1,632; 

 and the former number divided by the 

 latter, and half unity subtracted from the 

 quotient, gives 10.88 for the expectation 

 of the ag'e of 65. In this manner the fol- 

 lowing table is formed. 



TABLE II. 



Shewing the Expectations of Human Life at every Age, deduced from the Nor- 

 thampton Table of Observations. 



These tables suggest an easy method 

 of finding the number of inhabitants of a 

 place from the bills of mortality ; for, sup- 

 posing the yearly births and deaths equal, 

 it is only necessary to find, in the way 

 above described, the expectation of an 

 infant just born, and this multiplied by 

 the number of yearly births will be the 

 number of inhabitants. 



From all the observations which have 

 been made on the bills of mortality of 



different places, the faet is fully ascer- 

 tained, that the duration of human life is 

 greater in all its stages in country parishes 

 and moderate sized towns, than in large 

 and crowded cities. According to Simp- 

 son's correction of Smart's Table for Lon- 

 don, only one in 44 of the inhabitants at- 

 tain to the age of 80 years; Dr. Pi*5ce 

 gives the proportion somewhat greater, 

 or about 1 in 40, but observes that of those 

 who are natives of London, a much less 



