The second difficulty is harder to overcome. Propellers are most efficient when they are run at comparatively slow speeds. Those on the _Majestic_ are no exceptions to this rule, and at full speed are run at about one hundred eighty revolutions per minute. Turbines, however, are high-speed machines, capable generally of thousands of revolutions per minute. In order to utilize the power generated by the rapidly revolving turbine and transpose it into useful energy for use by the slowly turning propeller there must be some sort of reduction gear. The United States Navy has designed a number of its newest ships with an electric drive in which the high-speed turbines are used to generate electricity which is used to turn slow motors that drive the propellers. Another method is a reducing gear, similar in the work it does to the gears used in automobiles for “low” and “intermediate,” but necessarily very much greater in size. In the _Majestic_ the arrangement is of the latter type—that is, the turbines are operated at high speeds, and through a series of gears the propeller shafts are turned at slower speeds. [Illustration: THE _GEORGE WASHINGTON_ _An American liner, formerly a German ship. She was taken over by the United States during the World War._] Necessarily, in operating ships of such size as these we are discussing, any wasteful methods would be very expensive. It is open to some question as to whether these huge ships are worth what they cost, for the margin of profit they show is very small, and the cost of operation and repair is huge.