August 30. 1883] 



NA TV RE 



421 



inclined through half a right angle. The cass or" the ' but an examination of the triple-branched curve of her 

 Daphne resembles this in the slowness with which the stability given in Fig. S shows that the analogy between 

 stability increases as the vessel is inclined, this slowness the two cases ends at quite a moderate angle of inclina- 

 being due to the same causes in both cases doubtless ; tion, say 30 to 31 degrees. In this figure (8) the curve A 



CURVES of STABILITY of PRISMATIC BODY of SQUARE SECTION 



DRAUGHT of WATER % s »• of DEPTH. 



A WITH CENTRE OF GRAVITY AT CENTRE OF FORM. 



1 FOOT ABOVE 

 2FEET .. 

 1 FOOT BELOW 



2FEET ,. 



is constructed on the assumption thit the ship was free to 

 take wa'er on board as the main deck became immersed ; 

 the branch n presumes the poop to have been watertight ; 

 and the branch c is calculated to show how the stability 



curve would have increased until the bulwarks came 

 under water, provided these bulwarks had been water- 

 tight. It will at once be seen that the Daphne cannot be 

 regarded as analogous to the Hammonia or to the curve 



FIG. 5. 



CURVES of STABILITY of PRISMATIC BODY of SQUARE SECTION 



WITH CENTRE OF GRAVITY AT CENTRE OF FORM. 



A. WITH DRAUGHT OF WATER #i'J« OF DEPTH. 



^90° 



B in Fig. 5, in so far as the stability at very lar^'c angles 

 is concerned. On the contrary she would hive more re- 

 sembled the case of Fig. 6, provided her sides had gone 

 as high as her topsides and been there decked over. The 



Daphne's curve A ceases to rise soon after the main deck 

 becomes immersed, and then falls rapidly away in the 

 same manner and for the same reason as all ships lose 

 stability when, or soon after, the freeboard has become 



FIG.6. 



CURVE of STABILITY of PRISMATIC BODY of SQUARE SECTION 



DRAUGHT of WATER % "l> of DEPTH. 



WITH CENTRE OF GRAVITY 6 INS. BELOW THE HETACENTRE. 



40" 45 5 50 



exhausted. It must therefore be clearly understood that 

 it is in the early stages of the two curves that the cases 

 which I have had to make public find their resemblance ; 

 at the later stages the Daphne illustrates the consequences 



of the immersion of the deck, while the Hammonia, by 

 losing all stability before the deck became immersed, 

 opened up a state of things which startled her builders, sur- 

 prised the profession, and confounded the text-books, and 



