You don't get the interest compounded though, this isn't a bank account, it's payment on a bond. You'd have to find other south sea bubble bond holders to sell

You don't get the interest compounded though, this isn't a bank account, it's payment on a bond. You'd have to find other south sea bubble bond holders to sell you their bonds (which would only be done in whole units, you wouldn't be able to dribble in your 4% every year) to get the compound effect. Basically you look at the interest paid over the whole issue yearly and linear sum it, not apply a compound interest calculation.