PEOGRESS IN MAEINE CONSTRUCTION GRACIE. 691 



class, and 780 third-class passengers. Four hundred pounds was 

 charged for a suite of rooms. 



The power transmitted per shaft in this vessel was about 25 per 

 cent greater than in the previous unit, and two three-crank quadruple 

 engines were fitted to each line of shafting in order to reduce the 

 dimensions of the cylinders and working parts, a scheme which lent 

 itself naturally to more complete subdivision into watertight com- 

 partments. This arrangement, which was also tried in some naval 

 vessels, was, however, not repeated in later practice. The machinery 

 of this ship exerts the largest power of any installation of reciprocat- 

 ing engines in the merchant service, the next advance in total effort 

 being with turbine machinery. 



Within the next few years there appeared the Gedric^ AmeHka, 

 and Kaiserin Augusta Victoria^ all about 680 feet in length, and car- 

 r^dng still further the development in number and extent of super- 

 structures, public rooms, and luxurious cabin accommodation. The 

 Amerilca had six decks above the water line, as compared with Carn- 

 pania''s four. In none of these vessels was high speed attempted. 



The further development of the reciprocating engine since the be- 

 ginning of the period under survey has been in the use of still higher 

 initial pressure and in the extension of the range of useful pressure 

 in the quadruple-expansion type of engine. The use of higher pres- 

 sure followed naturalh'^ upon the success of the triple engine, and 

 for pressures above 180 pounds per square inch the quadruple type 

 became necessary in order to take the fullest advantage of the in- 

 creased heat energy available in the steam. 



Compared with the gain in fuel economy effected by the triple- 

 expansion over the compound engine, the further improvement due 

 to the increase in steam pressure to 215 or 220 pounds is naturally 

 small, being about 7 to 8 per cent, and against this has to be put the 

 increased weight, cost, and upkeep of the quadruple type. For ships 

 trading on long voyages, and more especially for passenger ships, or 

 large units, where a four-crank engine would be fitted in any case," 

 on account of its greater smoothness in running, the quadruple engine 

 has now superseded the triple-expansion type; but in the case of 

 cargo carriers, where low first cost and easy supervision are primary 

 conditions, the triple engine still holds its own. 



In the essential design of the reciprocating main engine, improve- 

 ments seem difficult to attain. Some changes, however, may be 

 noted. Condensers are now usually kept separate from the main 

 framing, and, in order better to withstand extremes of temperature, 

 are frequently constructed of mild steel, instead of being cast as 

 formerlj^; much more attention is also given to their design, with 

 a view to improve thermal results. Air pumps have been improved 

 in desig-n, and in most large or fast- running machinery are now 



