When a ship is being lifted it sometimes happens that
the load is not evenly distributed on the platform. Some
rams, therefore, may carry a full load, while others are much
underloaded. The platform is kept level by means of specially
designed valve gear operated by the moving rams in such
a manner that when one ram has a light, load it moves
ahead of the others, but in doing so lifts a lever and closes
its inlet valve, so that the rams are practically stopping and



RECENT ACHIEVEMENTS. 339

Starting dependent upon the load which may come upon
them, the valves being opened and closed automatically by
the movement of each of the rams. The valve box is
secured on the ram itself and moves up and down with it,
the inlet and outlet pipes working through stuffing boxes in
the usual manner.
The application of hydraulic power for effecting the open-
ing of the bascules of the Tower Bridge over the Thames
at London is shown in Figs. 191, 192, 193, and 194.
