Note 29 — Chapter IX · THE CREW OF THE SUBMARINE
Reading edition
A floating dock is built with a water compartment on each side and a platform on the bottom, thus leaving a large open space in between to hold a submarine or other vessel. By partly filling the compartments with water the platform sinks into the water deep enough so that the vessel can pass over and on top of it; then by pumping the water out of the compartments the floating dock is raised and the platform with the vessel on it is lifted out of the water where she can be examined and repaired if necessary.