170 ESSAY ON PROBABILITIES. 



much better than those of the Northampton table. 

 The male and female lives of the latter are nearly equal 

 in number ; the former is almost entirely founded upon 

 male lives : while the former, with its male lives only, 

 gives a longer duration of life than the latter. For 

 old lives, however, the Northampton table gives a some- 

 what longer duration than the Amicable. This is only 

 one fact out of many which show that the Northampton 

 table, while it gives much too great a mortality to the 

 younger class of lives, errs in the other extreme as to 

 the older. Of thirty-five tables, made in different 

 countries and at different times, and including all of 

 any celebrity which had appeared before 1830, I find 

 that the Northampton table is the eighth from the 

 lowest at the ages of 10 25, and the tenth from 

 the highest at the age of 65. The same may be said 

 of De Moivre's hypothesis, which the Northampton 

 table closely follows. 



The Northampton and Amicable tables are decidedly 

 older as to the period at which their members lived, 

 than the Carlisle and Equitable. Life is shorter in the 

 former pair than in the latter, while both of the former 

 agree in presenting the older lives comparatively better 

 than the younger ones, as compared with the latter 

 pair. By the Northampton table, the duration at 65 

 years is about a third part of that at 25 ; while the 

 same proportion is decidedly less in the same ages of 

 the Carlisle table : a similar result appears in the 

 Amicable and Equitable tables. I remember remarking 

 the same phenomenon in the results of a comparison of 

 the lives of naval officers. There can be little doubt that 

 the reason is as follows : in circumstances which create 

 a large mortality at the younger ages, all the feeble 

 constitutions are prevented from attaining old age, so 

 that the lives which really arrive at advanced years are 

 the remains of the very best lives. I saw the ocur- 

 rence of the same disproportion in the lives of officers 

 of the Anglo-Indian army; in which, however, it was 

 probably increased by the residence of many of the 



