Page:PettyWilliam1899EconomicWritingsVol2.djvu/318

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623
Duplicate Proportion.

Age, Now whether these be sufficient reasons, is not the present Enquiry; but taking the afore-mentioned Assertion to be true: I say, that the Roots of every number of Mens Ages under 16 (whose Root is 4) compared with the said number 4, doth shew the proportion of the likelyhood of such mens reaching 70 years of Age. As for example; 'Tis 4 times more likely, that one of 16 years old should live to 70, then a new-born Babe. 'Tis three times more likely, that one of 9 years old should attain the age of 70, than the said Infant. Moreover, 'tis twice as likely, that one of 16 should reach that Age, as that one of 4 years old should do it; and one third more likely, than for one of nine. On the other hand, 'tis 5 to 4, that one of 26 years old will die before one of 16; and 6 to 5 that one of 36 will die before one of 26; and 3 to 2, that the same person of 36 shall die before him of 16: And so forward according to the Roots of any other year of the declining Age compared with a number between 4 and 5, which is the root of 21, the most hopeful year for Longævity, as the mean between 16 and 26; and is the year of perfection, according to Our Law, and the Age for whose life a Lease is most valuable. To prove all which I can produce the accompts of every Man, Woman, and Child, within a certain Parish of above 330 Souls; all which particular Ages being cast up, and added together, and the Sum divided by the whole number of Souls, made the Quotient between 15 and 16; which I call (if it be Constant or Uniform) the Age of that Parish, or Numerus Index of Longævity there. Many of which Indexes for several times and places, would make a useful Scale of Salubrity for those places, and a better Judg of Ayers than the conjectural Notions we commonly read and talk of. And such a Scale the King might as easily make for all his Dominions, as I did for this one Parish.

 
The Sixteenth Instance.

In the Price of several Commodities.

Suppose a Mast for a small Ship be of 10 inches Diameter, and as is usual, of 70 foot in heighth, and be worth 40s; then a Mast of 20 inches through, and double length also, shall not