688 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



varies greatly on the different trade routes. It is notably greatest 

 upon the Atlantic, and in this trade we find the most rapid growth in 

 dimensions. 



It is the continued aim of the naval designer to realize the greatest 

 dimensions which the shipowner can utilize on the least possible 

 weights of hull, machinery, and fuel. Every improvement in the 

 quality of materials, every advance in the better distribution of those 

 materials toward the end in view, every reduction in the weight of 

 machinery and of fuel in relation to horsepower, and every pro- 

 gression toward the more effective use of the power developed, is 

 a step toward the ideal large, powerful, and comparatively light 

 vessel. 



The introduction of iron about the year 1820, of steel about 1870, 

 of the compound engine in 1854, and of the triple-expansion engine 

 in 1881, were the most notable epoch makers of the first 80 years of 

 steam navigation. The study of the strength problem by means of 

 the " girder " theory and the labors of the classification societies have 

 shown how to combine strength with lightness. The introduction 

 of the experimental tank method of research gave us a definite means 

 of designing form and propellers, so that the least possible amount 

 of power is wasted and the greatest possible amount is usefully 

 apx3lied. 



Up to the beginning of the period under consideration the changes 

 Avhich had taken place in marine engineering had been shown in a 

 gradual development of the simple type of reciprocating steam 

 engine. The growing knowledge of the theoretical principles in- 

 volved in design, the higher standard of materials available for 

 construction, and the steady improvement in machine tools, had 

 enabled engineers successfully to make use of higher steam pressures. 

 The advance marked by the successful introduction of the compoimd 

 engine about the year 1854 had been followed in 1881 by the intro- 

 duction of the triple-expansion type of engine, and the three-crank 

 design of the latter proved itself so fit a variation that it has sur- 

 vived, unchanged in all essentials, to the present day. Thus 20 years 

 ago the triple-expansion engine was in the position of rapidly super- 

 seding the compound type in almost all services, and was being suc- 

 cessfully constructed to work in conjunction with steel cylindrical 

 boilers working at a pressure of 160 pounds per square inch; both 

 engines and boilers being, in general design, not greatly different 

 from those of the same type which are being built at the present 

 time. 



I can best convey to you the condition of marine construction at 

 the beginning of the 20-year period immediate^ under review by 

 recalling some of the most notable achievements of that time. 



