[ I7I 3 
tions. In the infant ftate, under 2 years of age, there 
is one-fifth loft by death; but afterwards, as they 
gather ftrength, the deaths are diminifhed till be- 
tween 10 and 20; and from that age the mortality 
gradually increafes, till after the age of 40 ; when 
the number of the dead continues nearly the fame, 
though the probability of life continually decreafes 
till the age of 80 ; and then at length, the living be- 
ing almoft all exhaufted, the burials are greatly di- 
minillied. All which feems to be agreeable to the 
courfe of nature ; but, contrary to what we fee in 
the London bills, efpecially after fo years of age, as 
we have already obferved. However, they both agree 
in this, that the moft healthy age is between 10 and 
20, and the infant ftate under 5 years of age the 
moft uncertain for life. 
But indeed it muft be acknowleged, that in com- 
puting the Breflau table, Dr. Halley had great ad- 
vantages, which have made it fo perfe(ft. He had 
the number of births given, befides the burials at 
the different ages, in an inland town, where there is 
no great concourfe of ftrangers. But with us at 
London the number of births is not known; be- 
caufe of the number of diffenters of various deno- 
minations, both foreigners and natives, of whofe 
baptifms there is no account taken ; which makes 
our bills at prefent very imperfedt. For none are put 
into our bills but thofe who are baptized, according to 
the form of our eftablilhed church. And therefore 
there are fome thoufands omitted, and yet many, 
perhaps the one-half of them, who are not baptized 
with us, bury with us ; which greatly perplexes our 
bills. And under this difadvantage it appears very 
Z 2 difficult 
