PRESIDENTIAL ADDRESS. 7 
bladed bronze screw propeller about 23 feet in diameter. 
The crank shafts and the thrust shaft, 25 inches in diameter, 
are made of nickel steel; the screw shaft, 254 inches in 
in diameter, is of crucible steel, and the whole connecting 
shafting is of Siemens-Martin steel. Steam is supplied by 
twelve double and seven single boilers, working at a pres- 
sure of 213 pounds per square inch, and having 107,643 
square feet of heating surface. The 124 furnaces have 
3121 square feet of grate area. The boilers are arranged 
in four groups, each having a funnel of 16 feet in diameter 
and 131 feet above the keel. The boiler rooms are ventil- 
ated with cowls and eight powerful fans. There are in all 
79 engines on board including the main engines, and 124 
steam cylinders. | 
The use of steam jackets, re-heaters, and superheating 
apparatus for the purpose of the reduction of cylinder con- 
densation have shewn that steam jackets are not very 
efficient with modern high speed engines, that reheaters 
produce economy mainly in reducing the loss of power in 
the low pressure cylinder, and that superheating the steam 
appears to be the most satisfactory method provided that 
the final temperature does not exceed 500° F. 
The modern method of using auxiliary engines for con- 
densers, the use of feed water heaters, economisers, etc., 
have resulted in a considerable reduction in the cost of 
steam power. The characteristic features of modern steam 
machinery are the use of large units, high steam pressure, 
compound engines of moderate rotative speed for central 
station engines; triple and quadruple expansion marine 
engines, independent condensers and other auxiliaries, with 
steam exhausted non-condensing through feed water 
heaters, water tube boilers generally provided with super- 
heating attachments; economisers in the flues, high 
chimneys, and automatic stokers supplied with coal hand- 
ling machinery. 
