Page:The Steam Turbine.djvu/50

 !two-thirds of the disc area of the propeller, so as to present a very large bearing surface on the water, and this expedient effectually prevents its giving way under the force necessary to propel the vessel.

In models, and in vessels of moderate speed, the forces are not sufficient to tear

These were non-condensing turbines using saturated steam.

the water asunder, but if the pressure of the atmosphere is removed by an air pump, a model screw will cavitate at a comparatively moderate speed.