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XLIIL A Letter to James Weft, Efq\ Pre - 
fdent of the Royal Society , containing the 
Invejligations of Twe?ity Cafes of Com- 
pound Intereft , by J. Robertfon, Lib. 
R. S. 
S I R, 
Read Dec. t 3>TT is well known that the confideration 
of Compound Intereft is of great utility 
in the Computations refpedfing the values of Penfions, 
Annuities, Reverfions, and other affairs relating to 
Money concerns j and therefore, many Mathemati- 
cians have beftowed fome time on this ufeful fubjedt, 
and have endeavoured to difcover practical methods 
for folving the various cafes that might occur : And 
in thefe inquiries, the ufe of Logarithms has been 
found of Angular fervice in facilitating the operations. 
The late William Jones, Efq; F. R. S. among 
the variety of Mathematical matters to which he gave 
attention, confidered the bufinefs of Compound In- 
tereft fully, and did, many years ago, caufe to be 
engraved on a Copper-plate, more cafes in Intereft 
than had been exhibited before that time : Several 
copies of impreflions from that plate were diftributed 
among his friends ; to whom it appeared that he had 
treated this fubjeft in a more extenfive manner 
than had been done by other Mathematicians. 
The 
