C 17s 3 
by ii9fo, or more. And therefore above iiooo of 
thofe between 40 and yo, muft have retired from 
town. 
But now, as our bills are defediive, it is next to be 
conlidered, what we at London are to do at prefent, 
and what method of computation we are to follow ? 
And I imagine it is very obvious what may be done. 
Our bills may be ufed fo far as 14 or 20 years ; for 
there is certainly no increafe of our people till the 
age of 1 4 i becaufe few young people come to town 
till they are fit to be apprentices or fervants. And be- 
tween 14 and 20, though many come at that time, 
yet there is an emigration of a great number from 
hence to fea, to other countries, the univerfities, 
and country academies, that nearly balances the ac- 
ceffion of Grangers. And then, after 20 years of 
age, I believe the Breflau bills will be fufficiently cor- 
redt, to fhew the probability of life within and about 
the city. And if fo, a table may be made from both 
bills, that will agree with our cafe here with fufficient 
exadlnefs. For I cannot find, that there is any dif- 
ference in the bills, above the age of 20, that can be 
depended upon. And I fee no reafon why our air 
fhould not agree, as well with thofe in advanced life, 
as that at Breflau, and onr people be equally healthy. 
And this is not mere conje<Sure ; for, as far as I can 
examine into it, a j/zvitiy of things feem to con- 
firm it. 
Breflau is nearly in the - fame parallel of latitude 
with London, and therefore their feafons cannot be 
very different j and it is a large town, containing 
above thirty thoufand inhabitants, according to Dr. 
Halley 5 and fo the air, and circumflances of life, can- 
not 
