•1871 .] of Weight and Support in Ships . 293 



and Dr. Young, the author proceeds to show that the introduction of steam 

 as a propelling agent, and of largely increased lengths and proportions for 

 ships, has brought about a comparative distribution of weight and buoy- 

 ancy very different from that which those writers contemplated. He has 

 taken the cases of three or four typical modern ships, and has had the re- 

 lative distributions of the weight and buoyancy very carefully and fully 

 calculated and graphically recorded. Owing to the great labour involved, 

 only the most meagre and unsatisfactory attempts to measure and exhibit 

 the actual strains of ships had previously been made ; and the author's 

 results are wholly unlike any that have before been worked out and published. 

 The first case is that of the royal yacht s Victoria and Albert/ which re- 

 presents the conditions of long fine-lined paddle-steamers, with great 

 weights of engines, boilers, and coals concentrated in the middle, combined 

 with very light extremities. The second case s that of the * Minotaur/ 

 which represents long fine-lined ships with great weights distributed along 

 their length. The iron-clad ' Bellerophon ' is the third case, representing 

 shorter ships with fuller lines and very concentrated midship weights ; and 

 the last case is that of the ' Invincible 5 class, in which the weights of 

 armour &c. are still more concentrated. All these ships are divided into 

 very numerous short lengths ; and the weight of hull, weight of equipment, 

 and buoyancy or displacement of each short length are separately calculated, 

 curves of weight and buoyancy being constructed from these items used as 

 ordinates. A third curve, of which the ordinates are the differences be- 

 tween the curves of total weight and of displacement, known as the curve 

 of loads, is constructed. By summing the ordinates, or calculating the 

 areas of this curve, from point to point, a curve of shearing or racking 

 forces is formed ; and by employing the products of the areas of the curve 

 of loads (taken step by step) into the distances of their centres of gravity 

 from one end as ordinates of a new curve, a curve of bending-moments is 

 constructed. 



These operations are performed for all the ships previously named, first 

 when they are floating in still water, next when they are respectively float- 

 ing on the crests of waves of their own lengths, and thirdly when they are 

 floating in the hollow of two adjacent waves of those lengths. The maxi- 

 mum breaking-strains of all the ships when supported on shore, first at the 

 extremities and next at the middle, are also calculated, and compared with 

 the still-water and sea strains. 



In considering still-water strains, the author shows that remarkable con- 

 trasts of strain occur between ships light and laden, and that the theories 

 of former writers on the subject require to be greatly modified. In some 

 cases the breaking-strain is increased as the ship is lightened. In dis- 

 cussing the shearing-strains, he points out that the sections of maximum 

 shearing-strain in a ship coincide with the balanced or " water-borne sec- 

 tions" (at which the weight and buoyancy are equal), and that in most 

 ships the number of these sections is equal. The position of absolute 



