Chase.] -*-" [Februarys, 



returns of the Board of Health, and of the several monthly meetings of 

 the Society of Friends in the city and its immediate neighborhood. 



The general Philadelphia table is more extensive than any table hith- 

 erto published for a single locality, being based upon records of 435, 503 

 interments, 365,590 births, and seven successive decennial census enu- 

 merations. 



The Friends' table is based upon records of 14,666 interments, 4,364 

 births, and eight enumerations of membership. This is the first table 

 ever published that affords any basis for estimating the sanitary advan- 

 tages of moderation, temiserance, and a general regard for the laws of 

 health and morality. The tables which have been constructed from the 

 experience of different Tontines and Life Insurance Companies exhibit 

 some of these advantages, with the added indeterminate advantage of 

 medical selection. 



The following definitions and explanations may facilitate the study of 

 the tables : 



The possible life, is the limit which is sometimes attained in a given 

 district. 



The probable life {"vie probabW''), is the term at which one half of 

 those who are born alive will have died. It is the age, the probability 

 of living beyond which is as great as that of dying before the age is 

 attained. 



The probable life at any age, is the term at which one half of those who 

 are living at that age will have died. 



The expectation of life {'■'■me moyenne''''), is the average age which will 

 be attained by all who are born. 



The expectation of life at any age, is the average after life-time of all 

 who are living at that age. 



The mean expectation is the average after life-time of all who are living. 



The proportionate mortality at any age, is the ratio of the number 

 dying during the year following that ?ge to the number living at the 

 precise age. 



The mtality at any age, is in inverse ratio to the proportionate mortal- 

 ity at that age. If, for example, out of 1000 children born alive the average 

 number of deaths under 1 year of age is 180.38, the proportionate mor- 

 tality per 1000 is 180.38, and the vitality is ^-"-^ or 5.54. 



Neither the mean age at death nor the mean age of the living furnishes 

 a sufficient clue to the expectation of life, or any independent criterion of 

 salubrity. Emigration, immigration, excess of births over deaths or of 

 deaths over births, zymotic diseases, and other circumstances, variously 

 disturb the normal values which are embraced in a perfect life table. 

 Such a table represents an ideal stationary population, or one in which 

 the number of annual births is exactly equal to the number of annual 

 deaths, and one which is not affected by emigration or immigration. 



