To design a ship in this case and every other is plainly a matter of compromise, a quest of the optimum by a balancing of demands for safety, strength, speed, capacity, handiness, good behavior in a sea-way, so that each invested dollar may in the long run earn the largest return possible. Excellent examples of judicious design are the best passenger steamers plying between Europe and New York. Usually their section amidships is like that of a cargo vessel, but for a special reason. Within the freighter’s walls the greatest feasible cross-section must be created; so that the shape is box-like; in a high-speed passenger ship the form is also square, because harbors are shallow; were they less shallow the designer would choose a midship section somewhat semicircular in contour. Were our harbors deepened, the easy sections of the first transatlantic steamers could be repeated in their gigantic successors of to-day, with increased speed for each horse power employed. What a designer can do when his aim is swiftness at the expense of all other considerations, is shown in the lines of the torpedo-boat destroyer, page 62. Its length over all is 246 feet; length at water level, 240 feet, 10 inches; beam, 22 feet, 3 inches; mean draft, 6 feet, 1-1/2 inches; displacement, 489 tons; speed, 30 knots. It is interesting to contrast, on page 63, the cross-section amidships of this vessel, with similar lines of three other typical vessels described in this chapter.[6] [6] In writing these pages on the forms of ships I have been much indebted to Mr. Harold A. Everett, Instructor in Naval Architecture, Massachusetts Institute of Technology, Boston. G. I. CHAPTER VI FORM--_Continued_. SHAPES TO LESSEN RESISTANCE TO MOTION Shot formed to move swiftly through the air . . . Railroad trains and automobiles of somewhat similar shape . . . Toothed wheels, conveyors, propellers and turbines all so curved as to move with utmost freedom. Projectiles and Vehicles of Like Pattern.