WEIGHT AND SUPPOKT IN SHIPS. 
459 
the strains brought upon it. I will pass over the facts respecting the breakage in the 
older classes of wood ships, and confine attention to modern wood ships. Speaking of 
merchant vessels, Mr. Grantham says*', “It is the general custom with builders to leave 
the gangways of the bulwarks in modern ships unfinished, lest the hull should so much 
alter in form by settling in launching that the rails would not again fit their places ; 
and no builder would willingly copper a vessel when new, but rather allow her first to 
find her own position in the water, as she would then be less liable to wrinkle the sheets.’’ 
In wood-built ships of war there is also a considerable amount of breakage, as the fol- 
lowing facts will show. Our finest screw line-of-battle ships, of which the length was 
about 260 feet, broke, on the average, about 2 inches, some ships proving weaker than 
others, and the breakage in one case (that of the ‘ Gibraltar ’) amounting to 4 inches on 
a length of 200 feet. Our finest screw frigates, which are 300 feet long, broke from 
3 to 4 inches; the ‘Galatea,’ 280 feet long, broke 3 inches. Shorter ships, of course, 
usually broke less than these long fine ships. Iron ships, I need hardly say, display very 
little change of form or breakage when launched, the character of the materials and 
fastenings used in their construction being so much less yielding than those employed 
in wood ships, so that they resist more successfully strains of equal intensity. 
The severest strains connected with the launching of ships are, however, those which 
occasionally result from partial launches. The well-known case of the early iron ship 
‘ Prince of Wales’ illustrates this statement ; as, owing to an accident to the launching- 
gear, she was left for some time with her bow resting on the edge of a wharf and her 
stern supported by the water — in fact suspended by the extremities ; but although so 
severely strained no breakage took place. Another case in point is found in the wood 
line-of-battle ship ‘ Csesar,’ which stopped on the launching-ways at Pembroke Yard in 
1853, and remained for seventeen days with about 64 feet of the stern unsupported by 
ground-ways. The result was that the stern drooped about 2 feet in a length of 90 feet. 
A similar but more recent case of stoppage in launching is that of the iron-clad frigate 
‘Northumberland,’ which in March 1866 stopped with about 52 feet of the after part 
unsupported, and remained in that position for thirty days. The weight of the unsup- 
ported part may be roughly estimated at 440 tons, and the moment of this weight about 
the aftermost point of support at 11,700 foot-tons. At the corresponding station in the 
‘ Minotaur,’ when afloat in still water, the bending-moment is about 9200 foot-tons, and 
when supported on the crest of a wave of her own length, the bending-moment is about 
12,000 foot-tons. Now the ‘ Northumberland,’ although a sister ship to the ‘ Minotaur,’ 
has had her disposition of armour altered to the central-battery-and-belt system, and by 
this means rather more than 100 tons weight of armour and backing have been removed 
on the 52 feet of length from the stern forwards. The effect of this may be fairly 
assumed to be a reduction of the still-water bending-moments at the station in question 
to about 7000 foot-tons, and of the bending-moments on the wave to 10,000 foot-tons; 
and hence it follows that the strains resulting from the stoppage in launching in her 
* At page 92 of his work on ‘ Iron Shipbuilding.’ 
