578 THE PROGRESS IN STEAM NAVIGATION. 



tjiiialler vessel, as a matter of fact, was designed for a nuiximum speed 

 of "20^ knots, and the larger for 22 knots. Unless other qualities had 

 been sacritieed neither space nor weight could have been found in the 

 smaller vessel for machinery and coals corresponding to 22 knots. The 

 figures are interesting, however, as illustrations of the principle that 

 economy of propulsion is favored by increase in dimensions as speeds 

 are raised. 



Iti (>, 000 7, 500 



IN ' 9,000 11,000 



20 U, 000 15, 500 



22 23, 000 i Zi,m) 



Going a step tartiicr. it may be assumed that in unsheathed cruisers 

 of this class al)out 40 per cent of the displacement will be recjuired for 

 the hull and fittings, .so that the balance, or •'disposable weight," 

 would be about «>•» per cent, .say, 6. ♦»<)(> tons for the smaller vessel and 

 8,500 tons for the larger, a gain of nearly 2,000 tons for the latter. If 

 the .speed of 22 knots were secured in both ships, with machinery and 

 boilers of the same type, the larger ship would, therefore, hax'e about 

 2,000 tons greater weight available for coals, urmament, armor, and 

 equipment. The.se illustrations of well-known princi[)les have been 

 given simi)ly for the assistance of those not familiar with the sul)iect, 

 and they need not be carried farther. More general treatment of the 

 subject, based on experimental and theoretical investigation, will be 

 found in text-l)ooks of na\al architecture. 



SWIFT TOlll'EDO VESSELS. 



Torpedo flotillas nvv comijaratively recent additions to war fleets. 

 The first torpedo boat was built by Mr. Thornycroft for the Nor- 

 wegian navy in 1ST8, and the same gentleman l)uilt the fii-st torpedo 

 boat for the royal navy in 1877. The construction of the larger class, 

 known as •'torpedo-boat destroyers," dates from 181)3. These various 

 classes furnish some of the most notable examples extant of the attain- 

 ment of extraordinarily high speeds for short periods, and in smooth 

 water, b}^ vessels of small dimensions. Their qualities of perform- 

 ances, therefore, merit examination. Mr. Thornycroft mav jus^tly be 

 considered the pioneer in this class of work. Greatly impressed by 

 the combination of lightness and power embodied in railway loco- 

 motives, Mr. Thornycroft applit^l similar ])rin('iples to the propulsion 

 of small boats, and obtained remarkably high speeds. His work 

 became more widely known when the results were published of a 



