1869.] ^^ [Chase. 



By a joint examination, in accordance with the formulas of De Morgan, 

 Davies and Farr, of the numbers living at any given age and the num- 

 bers dying at the same age, the disturbances to which all populations are 

 subject can be mostly eliminated, and results obtained which will afford 

 a proper basis for comparisons. 



There are, however, some elements of uncertainty which cannot be 

 removed by any method hitherto proposed. Among these are the fol- 

 lowing : 



1. The old and still mooted doctrine of climacterics, or critical periods 

 of life in which some great constitutional change is supposed to take 

 place, appears to derive some confirmation from such irregularities as the 

 alternate diminution and increase of proportionate mortality, in the Car- 

 lisle table, at the ages 21, 22, 31, 33, 46, 50, 89, 90, as well as from the 

 increase of expectation, in the Carlisle table from 91 to 95, in Quetelet's 

 Belgian table from 89 to 91, and in the Philadelphia table from 91 to 100. 



2. Wherever a population is affected by immigration, two classes of 

 disturbance may be looked for ; one arising froin the poorer class of 

 immigrants,' who live in the most vmhealthy neighborhoods, exposed to 

 privations and hazards which increase the mortality of infancy and youth; 

 the other from a better class, like our house servants, the agents of im- 

 porting houses, and persons of some property, who increase the average 

 vitality towards the close of life. 



3. In many places, especially in cities, almshouses and asylums for the 

 aged furnish comforts which tend to prolong life. The tendency is aided 

 by the freedom from care and anxiety, the infrequency of exhausting 

 mental effort, and the watchfulness of friends or nurses. •* 



4. In a Society with birthright membership, like the Society of Friends, 

 nearly all the deaths in infancy and youth may be entered on the records. 

 But after reaching maturity the ties of membership are often sundered 

 for various reasons, and many of the deaths in old age may escape notice. 

 The ratios of apparent mortality will thus be affected unfavorably, during 

 the whole course of life. 



According to the census of 1860, the foreign-born residents of Phila- 

 delphia constituted nearly thirty per cent, of the entire population. On 

 this account any comparisons with other life-tables either in infancy or old 

 age might convey an erroneous impression. But the mean expectation is 

 probably but little affected by the foreign element, and it may very 

 properly be considered in the following comparison with two of the most 

 celebrated and one of the most unfavorable foreign tables. 

 Comparative mean expectations : 



Price's London. 23. 70 years. 



Philadelphia 31.46 " 



Farr's English, No. 3, male 31.77 " 



" " female 32.33 " 



Carlisle 32.66 " 



Friends' 33.11 " 



