To ,74. I proceed as in common 
Addition. Add ,39 
The fum is 113. What is this fum? Why 
it is a 113 hundredth parts; for, there be- 
ing only two figures in either of the Deci- 
mals, it is evident, that when added together, 
the fum muft neceflarily confift of hun- 
dredths. But 113 hundredth parts make 
one entire hundred and 13 fractional parts 
of another hundred. The i therefore on 
the left hand ceafes to be a fraction: it be- 
comes what Arithmeticians call an Integer; 
that is, a whole number: fo that I muft 
point it thus 1,13. Hence the rule that in 
the addition of Decimals you muft point of 
as many figures as there are figures in. either of 
the numbers to be added. 
This rule you will find in all books of 
Arithmetic; but the authors of thefe books 
never give any reafon for the rule; it be- 
comes therefore a mere matter of memory 
and is foon forgotten. 
The ten figures ufed in vulgar and de- 
cimal Arithmetic are doubtlefs wonderful 
inftruments for the purpofe of calculation. 
Let us try however whether it be not poffi- 
ble to find other fymbols, which, by figni- 
F 2 fying 
