WEIGHT AND SUPPORT IN SHIPS. 
417 
Suez Canal. We usually find the weights of engines, boilers, and coals concentrated at 
some part of a ship. In a paddle-steamer they are found near the middle of the length, 
in full-powered screw-steamers rather abaft the middle, and in auxiliary screw-steamers 
very far aft. Wherever they come their weight obviously increases the downward 
pressure at that part very considerably ; in some cases they cause, while in others they 
exaggerate, an excess of weight over buoyancy, and in others they bring up the weight 
very nearly to an equality with the buoyancy. No general law can now be laid down 
for the strains of all ships, and no general statement can be made to include all the 
conditions in which any particular ship may be placed by means of variations in her 
stowage or in the weights she has on board. Having given the details of the weights 
and buoyancies of various parts, however, the calculation of the resulting still-water 
strains is practicable, but involves considerable labour. I have taken the cases of three 
or four typical ships, and have had the Distribution of the Weight and Buoyancy very 
carefully calculated and graphically recorded. Each example is a ship of modern type, 
and the results are wholly unlike any which have before been published. In fact, owing 
to the great labour involved, or to some other cause, only the most meagre and unsatis- 
factory attempts to discover and exhibit the actual strains of ships have previously been 
made and recorded. 
The first case represents the conditions of long fine paddle-steamers, of high speed, 
employed as yachts, or blockade-runners, or on other services where great cargo-carrying 
power is of comparatively minor moment. The case I have selected is that of the Royal 
Yacht ‘ Victoria and Albert,’ and the diagram in Plate XVI. fig. 1 has been prepared in 
order to indicate the distribution of weight and buoyancy. In making the calculations 
required for this purpose, the total length (300 feet) has been divided into 20-feet spaces, 
and transverse planes of division have been supposed to be drawn in order to form the fore- 
most and aftermost boundaries of the spaces. For each division of the ship the buoyancy, 
the weight of the hull, and the weight of the equipment have been determined ; and the 
sum of the two latter qualities of course gives the total weight of ship and lading for any 
particular 20-feet space. A base-line A B (fig. 1) has been taken to represent the ship’s 
length, and a series of equidistant ordinates has been erected, each ordinate representing, 
in position, the centre plane of a 20-feet space. The positions of the imaginary planes 
of division in the ship are indicated in the figure at the middle points of the parts of A B 
lying between the feet of the ordinates ; and the distance between consecutive ordinates 
is, I need hardly say, 20 feet on the scale by which A B is set off. Upon these ordinates 
there have been set off on a certain scale of tons per inch*, — (1) a length representing the 
buoyancy of the division of the ship with which the ordinate corresponds, divided by the 
length of the division ; the ordinate will therefore represent the average buoyancy of the 
division per unit of length : (2) a length representing in a similar way, and on a similar 
scale, the average weight of hull per unit of length for that division: (3) a length simi- 
larly representing the weight of hull and equipment for that division. Through the 
* The various scales employed in constructing the diagrams are specified on the respective Plates. 
