1900.] on High-Speed Navigation Steam Turbines. 245 



Let us consider the machinery on one side of the vessel only : the 

 steam from the boilers is admitted directly through a regulating valve 

 to the high-pressure turbine driving one shaft, it then passes to the 

 adjacent low-pressure turbine, driving its shaft independently, thence 

 it flows to the condenser, and both the shafts then drive the vessel 

 ahead ; the reversing turbine revolves with the low-pressure shaft, and 

 being permanently connected with the vacuum of the condenser no 

 appreciable resistance is offered to its motion under these conditions. 

 To go astern the ahead steam valve is closed and the astern valve 

 opened, admitting the steam from the boilers to the reversing turbine, 

 and reversing the direction of rotation of the inner screw shaft. 



On the other side of the vessel the arrangement is the same, and 

 it will be seen that she can be manoeuvred as an ordinary twin-screw 

 vessel, and with great facility and quickness. 



On her second preliminary trial about three weeks ago, the 

 mean speed of four consecutive runs on the measured mile reached 

 34 '8 knots, and the fastest run was at the speed of 35*503 knots, 

 which is believed to be considerably beyond the recorded speed of any 

 vessel hitherto built. The vessel was scarcely completed at the time of 

 this trial, and it is anticipated that still higher speeds will be realised 

 on subsequent and official trials.* The speed of 35 • 5 knots, or nearly 

 41 statute miles, represents about 11,000 indicated horse-power in 

 a vessel of 350 tons displacement, as compared with 6000 to 6500 

 developed in the 30-knot destroyers of similar dimensions and 310 tons 

 displacement. 



At all speeds there was very little vibration. Her speed astern is 

 guaranteed to be 15^ knots. 



The Viper has surpassed the Turbinia in speed, and is at the pre- 

 sent time the fastest vessel afloat. 



In regard to the general application of turbine machinery to large 

 ships, the conditions appear to be more favourable in the faster class 

 of vessels, such as cross-Channel boats, fast passenger vessels, liners, 

 cruisers and battleships ; in all such vessels the reduction in weight 

 of machinery, and the economy in the consumption of coal per horse- 

 power, are important factors ; the absence of vibration is also a 

 question of first importance, securing the comfort of passengers, and, 

 in the case of ships of war, permitting of greater accuracy in sighting 

 of the guns. 



The model exhibited represents a proposed cross-Channel boat for 

 the Dover and Calais or Newhaven and Dieppe routes. She is 270 

 feet length, 33 feet beam, 1000 tons displacement, and 8 feet 6 inches 

 draught of water. She has spacious accommodation for 600 passengers, 

 and with machinery developing 18,000 horse-power would have a sea 

 speed of about 30 knots as compared with the speed of 19 to 22 knots 

 of the present vessels of similar size and accommodation. 



* The Viper has sinre attained with full trial weights on board a mean speed 

 of 36-58 knots, on a one-hour's full-power trial, the fastest runs being at the rate 

 of 37 "118 knots per hour. 



