674 Transactions. — Miscellaneous. 



small watercourse), all with a view of lowering the centre of 

 gravity. In spite of this these vessels could never possess i.he 

 most important quality — viz., a good range of stability. It is 

 still abundantly evident that there is much need for a greater 

 diii'usion of sound information upon this subject, and for an 

 equally extensive use of it by shipbuilders. 



The Transactions of the Institution of Naval Architects 

 for several years past abound with papers upon this subject. 

 Instead of the old jealousy and desire for secrecy, competitors 

 in business have vied with each other in giving full explana- 

 tions of many new methods which they have adopted for 

 arriving at the desired results more quickly and certainly. 

 The naval architects at the Admiralty have also done equally 

 well, and have greatly advanced the interest which has been 

 taken in the science. 



It may be well to say a few words about bilge-keels or 

 rolling-chocks, as it is often stated that these add to a ship's 

 stability. This is quite an erroneous opinion. They are 

 always under water, and therefore cannot affect the position 

 of the centre of buoyancy at any degree of inclination. Their 

 functions are quite different from those of the " bolsters " 

 which were affixed to our circular model, for the simple reason 

 that the latter, being at or above the water-level, increased 

 by inclination the moment of the solid of immersion, and so 

 formed a righting-lever. The work which bilge-keels do is to 

 reduce the range and violence of rolling by presenting a drag 

 to the water. When rolling has ceased they simply do no- 

 thing. They increase the steadiness, but do not affect the 

 stability. 



I have purposely left a description of one of the most in- 

 teresting operations to the last. I refer to the method adopted 

 for finding the height of the centre of gravity of a ship. The 

 plan is a most ingenious one, and could not fail to interest 

 any one having a taste for figures, statics, or mechanics. It 

 will at 'once occur to every one that you cannot handle such 

 an object as a ship or suspend her from various points as we 

 can these models. Neither would it be possible to find it by 

 experimenting with ever such a carefully-prepared model, be- 

 cause no ship is homogeneous in structure, but every ship is 

 so complicated that no model could represent her as to the 

 weight of all her parts. While we are unable to lift and 

 suspend the ship, however, we know the laws which govern 

 the support which the water affords to her. We must there- 

 fore cause her to assume difi'erent positions in this element, 

 and then work backwards in order to get what we want. It 

 is necessary to measure the exact amount of power applied to 

 produce these changes of position. When we have found out 

 all the facts surrounding, so to speak, the one which we want 



