> Combine them all, and they could know where islands were that they couldn't see. I'm curious as to the range that these things could be detected. No doubt th

> Combine them all, and they could know where islands were that they couldn't see. I'm curious as to the range that these things could be detected. No doubt there's some proportionality between island size and distance-detectability. But there are a whole bunch (small) islands in the middle of a whole lot of nothing, so I'm curious to know how many were found on purpose and how many by accident.