Withy. — On the StaUlity of Ships. 673 



Now look at the change brought about by careening. The 

 centre of buoyancy moves to leeward to the position b, but the 

 centre of gravity naoves still further to leeward. The down- 

 ward pressure of the weight and the upward pressure of the 

 buoyancy are, it will be seen, both acting in the same direction 

 to overturn the log, because the metacentre falls below the 

 centre of gravity. Instead of a righting-lever it possesses an 

 upsetting-lever. These are the conditions which make it im- 

 possible for it to float on its side. It consequently assumes 

 the other position — viz., with one corner down. 



Let us now see by reference to fig. 7, Plate LI., why it 

 prefers this way. The centre of gravity is of course just where 

 it was, but the centre of buoyancy is at the point B. Now 

 look at it when inclined, and you will see that the centre of 

 buoyancy moves to leeward to b, and the perpendicular passes 

 to leeward of the centre of gravity, places the metacentre 

 above it, and thus forms a satisfactory righting-lever, and 

 resists the inclining force. 



This model will further serve to illustrate the case of the 

 " Captain." A very little more inclination than that shown 

 would bring its angle under water, and its range of stability 

 would fall off as a consequence, and its breadth at water-line 

 would continue to decrease until it would fall over. 



A very different variety of midship section from that of the 

 " Captain," but still a very objectionable one, is represented 

 in an exaggerated form in fig. 2, Plate L. The greatest breadth 

 is considerably below the water-line, and the tumble-home 

 starts from this point, and is large. Such a vessel may have 

 a fair amount of initial stability, although her metacentre 

 must be low ; but it is impossible that she can have a long 

 "range" of stability. About the year 1864 a batch of large 

 sailing-ships was built in the north of England for Liverpool 

 shipowners. They were all deep in proportion to beam ; their 

 greatest breadth was at one-third up, and they were heavily 

 rigged. They all required ballasting as soon as the builders 

 had run up their topmasts. One of them while loading coal 

 for her first voyage listed against the dock side until her yard- 

 arms touched the quay after she had taken in 800 tons, fully 

 half her lading. This one was lost off" the Hebrides on her 

 first voyage. Most, if not all, of the crew reached land in one 

 of the boats. The captain reported that, while sailing along 

 quite satisfactorily to all appearance, she took a further list 

 as the breeze freshened, and steadily settled down on her 

 broadside, just as the " Captain " did. The remaining ships 

 wdiich were not completed were altered as far as possible. 

 Several feet were taken off their lower masts, and in one or 

 two cases the space under the hold-ceiling between the floors 

 was filled in with bricks and cement (with the exception of a 



