568 THE PROGRESS IN STEAM NAVIGATION. 



best adapted for a torpedo ))oat or de.stro^-er. There is, in faet, no 

 general rule api)lical)l(^ to all classes of st«'anishi|)s; each must be con- 

 sidered and dealt with independently, in the light of the latest 

 experience and improvements. For merchant ships there is always 

 the commercial consideration. Will it pay? For warships there is the 

 corresponding inquiry. Will the cost be justitied by the power and 

 efficiency of the proposed ship? 



CHARACTERISTICS OF PROGRESS IN STEAM NAVKiATION. 



Looking at the results so far attained, it may be said that progress 

 in steam navigation has l)een marked by the following characteristics: 

 (1) (irowth in dimensions and weights of ships, and large increase in 

 engine power as speeds have been raised. {'2) Impro^■ements in marine 

 engineering, accompanying increase of steam pressure. Economy of 

 fuel and reduction in the weight of propelling a])panitus in pi-oportion 

 to the power developed. (;-i) Improvements in the materials used in 

 shipbuilding; better structural arrangements; relatively lighter hulls 

 and lai'ger carrying power. (4) Improvements in form, leading to 

 diminished resistance and economy of power expended in propulsion. 

 These general statements represent well-known facts — so familiar 

 indeed that their full significance is often overlooked. It w^oidd he 

 easy to nudtiply illustrations, but onh^ a few representative cases 

 will be taken. 



TRANS-ATLANTIC PASSENGER STEAMERS. 



Trans- Atlantic service naturally comes first. It is a simple case, in 

 that the distance to be coxered has remained practically the same, and 

 that for luost of the swift passenger' steamers cargo-carrying capacity 

 is not a very important factor in the design. In 1840 the Cunard 

 steamship Brltatund, luult of wood, propelled l)y paddle wheels, main- 

 tained a sea speed of about 8i knots. Her steam pressure was 12 

 pounds per square inch. She was 207 feet long, about 2,000 tons in 

 displacement, her engines developed about 750 horsepower, and her 

 coal consumption was about 40 tons per day, nearly 5 pounds of coal 

 per indicated horsepower per hour. She had a full spread of sail. 

 In 1871 the White Star steamship Ocean /<:\ first of that name, occu- 

 pied a leading position. She was iron built, propelled by a screw, and 

 maintained a sea speed of about 14^ knots. The steam pressure was 

 65 pounds per square inch, and the engines were on the compound 

 principle. She was 420 feet long, about 7,200 tons in displacement, 

 her engines developed 3,000 horsepower, and she burned about 65 tons 

 of coal per day, or about 2 pounds per indicated horsepower pei' hour. 

 She carried a considerable spread of sail. In 1889 the White Star 

 steamer Teutonic appeared, proyjelled by twin screws, and practically 

 with no sail power. She is steel built, and maintains a sea speed of 



