128 



ELECTRIC PROPULSION OF SHIPS. 



Table III. 



Relative Data, Group I. 



Relative Data, Group II. 



(b) With Babcock and Wilcox boilers. 

 (s) With Scotch boilers. 



It is of course known that the weights and other characteristics of machinery con- 

 structed by diiTerent builders vary considerably, which doubtless accounts for much of the 

 difiference between the conclusions of Mr. Thau and the above. 



These tables also indicate what is well known but often overlooked — that small engines 

 and machinery generally weigh less per horse-power than large machinery. These figures, 

 for the entire machinery installations, also generally correspond in this respect. 



With the conditions in merchant work such as to permit of building machinery on a man- 

 ufacturing basis, development would take place resulting in many improvements, and it is 

 conceivable that the relative improvement would favor the Diesel electric installation. 



The above outline installations are conservative in design and follow moderate prac- 

 tice. We know that some features of value might be incorporated to show more favorable 

 results in a discussion of this character, such, for example, as greater steam pressures, higher 

 superheat, double reduction gears, etc., but such installations require more careful operation, 

 and while they may show theoretically better results, under the ordinary prevailing condi- 

 tions, we would not now recommend them except where they are to be operated with the re- 

 quired knowledge and care. 



In regard to fuel, with the present development and conditions it is frequently neces- 

 sary to pay from 40 to 50 per cent more for Diesel engine fuel than for steaming oil fuel, 

 depending upon the trade. New advances are modifying these conditions. 



It will be understood that other arrangements in dissimilar vessels will work out some- 



