All About Engines

Engines for Ships 301 with the size of the man standing in the foreground. It is 18 feet 8 inches high, and the 9,353 brass tubes, 12 feet 6J inches long, give a cooling surface of 23,000 square feet. The main circulating pumps are capable of supplying to each condenser 18,500 gallons of cool- ing water per minute. They are of the centrifugal type, made by W. H. Allen, of Bedford. Weir Dual air pumps are used to maintain a vacuum of 28J inches when the barometer stands at 29 inches. No fewer than twenty-six fans are employed to ventilate the engine room, for which 700,000 cubic feet of fresh air per minute is provided. New Systems of Ship Propulsion While the turbine has no rival as a means of pro- pulsion for the fastest passenger ships and ships of war, there are objections to it for the slower cargo boats under less highly skilled control. Unless the turbine is made excessively large the speed must be very high, and the screw propeller is most efficient at moderate speeds. For the sake of economy and of space boilers must produce high- pressure steam, and turbine speeds must be as low as possible. Those of the Mauretania run at 700 revolutions a minute as compared with the 160 or thereabouts of even a respectable cargo boat driven by reciprocating engines. The turbine, again, is not very convenient for manoeuvring in a restricted space, and owing to its high speed reversal cannot be very rapidly effected. For these and other reasons, en- gineers have been casting about for methods of