Early in the eighteenth century, the French navigation expert, Pierre Bouguer, invented a log that was suspended below water at about 60 feet depth from a light surface float.
Kwangoko kwinkulungwane ezilishumi elinesibhozo zamaFrentshi kumkhosi wamanzi enolwazi kuPrerre Bouguer, Yabeka ilogo eyakeyayekwa phantsi kwamanzi ezingange nyawo ezintandathu.