The Operations of the Geometric and Military Compass

ly to the value of the ducat, that is to 124; and you will move the instrument no further. Then, whatever sum of scudi is proposed, you will transmute into ducats by taking the said sum transversally and measuring it directly. As for example, we wish to know how many ducats 186 scudi make: take 186 across, and measure it directly, and you will find 240, and so many ducats will the said scudi make.

We will be able to resolve the questions of this rule quite quickly with the help of the same arithmetic lines, and this in two different ways of operating, as we will make clear and manifest with the two following examples. It is sought how much 140 scudi will earn in 5 years at the rate of 6 per 100 per year, leaving the interest on the capital and on the other interests, so that they continuously earn: to find then what we seek, take directly the first capital, that is 140, and throw this transversally to 100. And without moving the instrument, take immediately transversally the distance between points 106, which is the 100 with the interest, and return to open the instrument again. And this interval, which you lastly took with the compass, throw it to 100, and opening the compass a little more, take transversally the distance between points 106, and with the instrument opened a little more again, throw this distance just now found to 100; and opening the compass, take the 106, and in sum.