ELECTRIC PROPULSION OF THE U. S. S. JUPITER. 197 



and I think tliat the statement which Mr. Emmet has made, in the next to the last paragraph 

 of his paper, is very broad. He says : "If my first design for a warship made over four years 

 ago had been accepted by the Navy Department, the vessel produced would have been very 

 greatly superior in respect to economy, reliability, weight, simplicity and cruising radius to 

 any ship now afloat, and ever since that time my case has been steadily strengthening through 

 the great improvements which have been made in high-speed turbines." In regard to econ- 

 omy we can rely, to some extent, upon certain calculations, although we do know that cal- 

 culations sometimes go astray. In regard to weight, the same thing applies there. In sim- 

 plicity, he might or might not be right; it depends whether marine engineers want a lot of 

 electrical devices to bother with. There are lots of men who succeed in the mechanical hne 

 who do not seem able to grasp electrical engineering. 



In regard to reliability, I ain surprised that a man of Mr. Emmet's ability and expe- 

 rience should make a statement of that character. In my short and limited experience, com- 

 pared with that of Mr. Emmet, I have found that reliability is something that we can tell 

 very little about until we have actually tried the machine in practice. I cannot understand 

 Mr. Emmet making such a statement. He might have reason to believe so, but that will not 

 make it more reliable in practice. 



In regard to economy, I do not think there is very much question but that the combina- 

 tion of the reciprocating engine exhausting into a turbine is the most economical unit ; the tur- 

 bine might be geared to its propeller shaft so as to get as high propulsive efficiency as possible. 



Mr. Emmet talks about putting all the reciprocating engine builders down and out. All 

 I have to say to that is this — he has not done so, nor do I think he will. The reciprocating 

 engine has not been perfected, and I do not think it will be for a great while — improvements 

 are being made on it all the time. 



Between the years 1896 and 1905 very little improvement had been made in the 

 economy of the reciprocating engine, except that due to the use of higher pressure of steam. 

 No attempt was made to decrease the clearances, to straighten the steam passages, etc., until 

 about the end of the abovcrstated time; in fact in some cases the ships that were built at the 

 latter part of this time had greater clearances than the earlier ones ; for instance the gunboat 

 Marietta (built in 1896) had about 16 to 17 per cent clearance in the high-pressure cylinder, 

 while the armored cruisers Washington and Montana (built about 1906) had about 

 28 per cent. 



When the Michigan and South Carolina were built some attention was given to cutting 

 down the steam consumption. In these engines the valve chests were lengthened, thus cutting 

 down the clearances and making straight steam passages instead of crooked ones. The steam 

 pressure was higher, and the range of expansion was greater, than in any previous battleship. 

 While there are no data on steam consumption of these two ships available, it is safe to state 

 (judging from their coal consumption) that these engines were greatly superior to any 

 battleship engines that had been built up to that time. 



The Delaware (which was completed shortly after the above-named ships) had engines 

 very similar to the Michigan. On the full-speed trial the water consumption was a little over 

 13 pounds per indicated horse-power per hour, while at 19 knots it was slightly under 13 

 pounds. 



Lieutenant-Commander Dinger estimates that in the combined system the water rate 

 can be cut down to 8.5 pounds per horse-power per hour. He takes as a basis for his esti- 

 mates two ships already built and tried. In the Delaware the steam pressure carried in the 



