BATTLESHIPS. EXPERIENCE GAINED ON THE JUPITER. 189 



In addition to the two advantages just stated, there are a number of other 

 things entering into a comparison of the two methods that make it very doubtful if 

 the mechanical gear would be as good, even at the high speeds, as the electric re- 

 duction. It would probably be necessary to use at least four turbines with a mechan- 

 ical gear instead of two with the electric method; this fact alone would make the 

 electric reduction the more efficient of the two. Then there are also the very con- 

 siderable losses due to the friction and windage of the backing turbine. According 

 to Sir Charles Parsons this loss amounts to about one-half a per cent. Also there 

 would be a saving due to the fact that only one set of auxiliaries would be used at a 

 time. 



Space Occupied. — As regards the actual space that the machinery would oc- 

 cupy, the electric drive would take up less space than any other installation, with 

 the possible exception of the mechanical gear. The arrangement of the ma- 

 chinery, however, is so much more flexible with the electric drive than with other 

 methods that it is probable it would occupy less space than would the gears. It 

 lends itself very readily to watertight subdivision. 



Weight. — The next point to be considered is that of weight, and here again 

 the electric drive is superior to any other method, with the possible exception of 

 mechanical gears. It is rather difficult to say exactly how the two methods would 

 compare either as regards space or weight, as a great deal would depend on the num- 

 ber of turbines used with the mechanical gear in order to get 30,000 shaft horse- 

 power. However, if the largest sizes of geared turbines now at sea are any guide, 

 the weight of the electric drive would be less than the weight of the geared 

 turbine. 



Care and Upkeep. — As regards care and upkeep, the electric drive is greatly 

 superior to either reciprocating engines or direct-connected turbines; also, due to 

 the fact that the turbines do not have to reverse, it would be superior to the geared 

 drive in that it would have less blading trouble. Either of the two latter methods, 

 however, is very satisfactory in this respect, as a high-speed turbine is so small 

 that it is easily handled and repaired by the ship's mechanics. 



This completes the case of the electric drive for battleships; all of the points 

 have been considered and in every case it has been seen that it has no superior. 

 There are, however, some points that have been made against electric propulsion, 

 and these will be taken up before proceeding to a discussion of the Jupiter's in- 

 stallation. First, there is the danger from large quantities of water in the engine- 

 room; however, this danger is more fancied than real, as all the wiring could be 

 placed well overhead, being taken out of the tops of the motors and generators. 

 The generators could be placed high enough to insure their safety and the motors 

 could be placed in watertight pits so that the engine-room could have enough water 

 in it to put the auxiliaries out of commission before reaching the main engines. 

 The next point is that, when operating with one turbine, all motors must run at the 

 same speed if they run at all ; this fact has been found to be no handicap in actual 

 operation. The next point is that, in turning, the inboard screw does not slow down ; 



