According to inventory records, the Portuguese navigator Ferdinand Magellan had 18 hourglasses on each of his ships during his circumnavigation of the globe in 1522. I’ve read this fact in more than one source, but no one tells us why eighteen. Multiple hourglasses would allow you to check one against another for accuracy, but 18 seems like a lot for that purpose. Were all 18 used at the same time? You need only one sandglass to cast a log—and that sandglass would count minutes, not a whole hour.
It seems Magellan used the hourglasses mainly for keeping track of time. But why did he need 18 of them?
If anyone can tell me I’ll draw you a picture.
Back to the beginning of The Western Civ User’s Guide to Time & Space