Royal Society. 43 
As ^<JiX53iX4^5, or 1^619099^^ ^^ N^i', to 8x8x9, or 
57(J, or Yyvy for the firfl year3 lb 0,9434, to 0,00000548. 
to 15X1(^X18, or 43 20, for the 2d year^ 100,8900, to 0,000024^2 
to 21X24X28, or 141 1 2, for the 3d year -lb 0,8396', to 3,00008128 
to 27X52X58, for the 4th year- lb 0,7921, to 0^000166^0 
to 33X41X48, for the 5th year 5 100,7473, to 0,00031071 
to 39X50X58, for the 6th year- fo 0,7050, to 0,0005 1051 
And fo on to the 6oth year, when we Ibppole the elder life of 
forty certainly to be expired j from whence till 70 we muft com- 
pute for the firft and fecond only, and from thence to 90 for the 
nngle youngeit life • then the lum total of all thefe fourth pro- 
portionals being taken out of the value of a certain annuity for 90 
years, being 16,58 year's purchafe, will leave the juft value to be 
})aid for an annuity, during the whole term of the lives of 3 per- 
sons of the ages propofed, and note, that it will not be neceffary 
to compute for every year fingly, but that in moft cafes every 4th 
or 5th year may fuffice, interpolating for the inteimediate years. 
It may be objected, that the different falubrity of places does 
hinder this propofal from being univerfal, which muft be al- 
lowed 5 but by the number that die, being ii-jj^'per annum \u 
34000, it appears that about a 30th part die yearly, as Sir Wil- 
Uam 'Petty hath computed for London j and the number that die 
in infancy is a good argument, that the air is but indifferently 
wholelbme ; ^lO that as far as appears, there cannot be a better 
place than ^reflaw propofed for a ftandard. 
To examine tbefrefinefs of Water; by Mr. Boyle. Phil. TranC 
2n1° 197. p. 627. 
H E honourable Mr. Soyle having found by various trials, 
that leveral metallic and other mineral Iblutions could be 
readily precipitated, not only by the fpirit of fait, but by crude 
fair, whether dry or diffjlved in water, it was no very difficult 
matter for him to think, that, by a heedful application of the 
precipitating quality of common lalt, one might difcover, whe- 
ther any particles of it, at leaft in any confiderable number, lay 
concealed in diftilled water, or any other propofed to be examin- 
ed: He took fome common water diftilled in glafs-veffels, that it 
might leave its fait, if it had any, behind it, and he put one 
grain of common dry fait into a thoufand grains of it ; into a con- 
venient quantity, as two or three fpoonfuls, of this impregnated 
]iq[uor, he let fall a fit proportion, for inftance 4 or 5 dropa, 
of a very ftrong and well filtrated folution of refined filver, 
difiblved in clear ^qua-fortisj upon which there immediately 
F z appeared 
T 
