57fi THE PROGRESS IN STEAM NAVIGATION. 



under which .sperd trials are made a iiu>ro stateiiuMit of speeds attained 

 is of no service. One requires to be informed accurately respecting 

 the duration of the trial, the manner in which eno-iiu's and boilers are 

 worked, the extent to Avhich boilers are "forced." or the proportion 

 of heating surface to power indicated, the care taken to eliminate the 

 influence of tide or current, the mode in which the o))servations of 

 speed are made, and other details, l)efore an}' fair or exact comparison 

 is possible between ships. For present purposes, therefore, it is pref- 

 erable to confine the illustrations of increase in speed in war ships to 

 results obtained under Admirality conditions, and which are fairly 

 comparal)le. 



A great increase in si/e has accompanied this increase in speed, but 

 it has resulted from other changes in modern types as well as from 

 the rise in speed. Modern battle ships are of 13,000 to 15,000 tons 

 and modern cruisers of 10,000 to 14,000 tons, not merely because they 

 are faster than their predecessors, l)ut because the}'^ have greater 

 powers of offense and defense and possess greater coal endurance. 

 Only a detailed analysis, which can not now be attempted, could show 

 what is the actual influence of these several changes upon size and 

 cost and how greatly tlu' improvements made in marine engineering 

 and shipl)uilding have tended to keep down the growth in dimensions 

 conse(|uent on increase in load carried, speed attained, and distance 

 traversed. It will l)e noted also that, large as are the dimensions of 

 many classes of modern war ships they are all smaller in length and 

 dis})lacement than the largest mercantile steamers above described. 

 Ther(> is, no doubt, a popular l)elief that tlu» contrary is true, and that 

 war ships exceed merchant ships in tonnage. This arises from the fact 

 that merchant ships are ordinarily desci-ilx'd. not bv their displac<'ment 

 tonnage, but by their register tonnage, which is far less than their 

 displacement. 



As a matter of fact, the largest battle ships are only of about two- 

 thirds the displacement of the largest passenger steamers, and from 

 200 feet to 300 feet shorter. The largest cruisers are from 100 feet 

 to 200 feet shorter than the largest passenger steamers, and about 60 

 percent of their displacement. In breadth the war ships exceed the 

 largest merchant steamers by from 5 feet to 10 feet. This difference 

 in forn' and proportions is the result of radical differences in the ver- 

 tical distribution of the weights carried, and is essential to the proper 

 stabilit}^ of the war ships. Here we find an illustration of the general 

 principle underlying all ship designing. In selecting the forms and 

 proportions of a new ship considerations of economical propulsion 

 can not stand alone. They must be associated with other considera- 

 tions, such as stability, protection, and maneuvering power, and in 

 the final result economy of propulsion may have to be sacrificed to 

 some extent in order to secure other essential qualities. 



