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XXVIII. A Letter to the Ri^ht Honourable 
o 
the Earl of Macclesfield, P ref dent of the 
Royal Society^ concerning the Method of 
conflruEUng a Lable for the Probabilities 
of Life at London, fro?n the Revere?^ 
William Brakenridge, D. £). a?2d F.R. S, 
My Lord, 
Read April 24, 'irx OU R charadler in the philofophi- 
*755- world, in the relation yon 
bear to each member of our illuftrious Society, makes 
me prefume to offer my thoughts to you, on a very 
interefting fubjedl, the probability of human life 
from the bills of mortality. For as it has fome dif- 
ficulty, and requires an accurate examination of many 
circumftances, I could not pofiibly fend fuch calcu- 
lations to any one who underftood them better, or 
could more quickly difcover any miftake, or falla- 
cious realoning ; and I hope your ufual goodnefs, 
and indulgence to every induftrious inquirer will ex- 
cufe me, that I give you this trouble. 
The great Dr. Halley, who had a fingular faculty 
of applying his mathematical knowlege to the pur- 
pofes of life, was the firft who particularly attended 
to this fubjedt. In the year idqa, from the bills of 
mortality at Breflau, he reduced it into a fort of 
fcience ; and gave a table of the probabilities of 
life, that hitherto has been juflly efteemed the mod: 
exacd: of any thing of the kind j from which he and 
others have deduced many propofitions, that are 
2 highly 
