220 Prof. F. Elgar. The Variation of 



and the dangers which may be incurred by low-sided ships are well 

 understood by many. In former times, it was not so necessary as ifc 

 has recently become, to carry theoretical investigations to the point 

 of ascertaining the angle at which a ship would capsize. It is only 

 during the last twenty years that small height of side out of water 

 has been thought a desirable quality for sea-going war-ships to possess, 

 or that certain classes of merchant vessels have been evolved in which 

 range of stability has been unduly limited by lowness of freeboard. 

 When Atwood wrote his papers, and for very many years after, war- 

 ships were built with such lofty sides, and merchant vessels were eo 

 comparatively uniform in type, and so deep in proportion to their other 

 dimensions, that no demand arose for complete curves of stability. 

 Besides, all the vessels of Atwood's day, and for long after, were 

 sailing ships ; and such few investigations as were made respecting 

 their stability, were for the purpose of determining their sail-carrying 

 power. The constructors of the old types of vessels judged of and 

 regulated stability by reference to the practical test of sail-carrying 

 power at sea, and this was usually sufficient for the purpose. 

 Modern variations of type, which began after the introduction of 

 steam, have for some time, however, rendered scientific calculations 

 necessary, which before were considered merely interesting or 

 curious. The many departures from the comparative uniformity 

 of proportions and form that once prevailed, and particularly the 

 extent to which some of these departures have gone in the direction 

 of reducing freeboard, have created the necessity referred to. 



Curves of stability, having been first produced for the purpose of 

 ascertaining the effect of low freeboard, and having disclosed the 

 dangers which lowness of freeboard may cause, have been largely 

 used for that purpose. If we consider the cross-curves of stability 

 or curves of righting moments for various draughts of water, the 

 angle of inclination being constant it will be seen that while the 

 upper and middle portions of those curves have been often dealt 

 with, the lower portions have been almost, if not quite, neglected. 

 The stability of a floating body at light draughts is, however, similar 

 in character to that at deep draughts, and the same peculiar features 

 and dangers that have been found to exist with low freeboard are 

 frequently connected also with lightness of draught. 



It fell to my lot to make some investigations respecting the 

 stability possessed by the " Daphne " at the time of the disaster 

 which befell her, and to give evidence respecting the same. I after- 

 wards, by way of explanation of a portion of the evidence, wrote a 

 letter to the " Times," which appeared on the 1st September last, 

 calling attention to the relation which exists between the righting 

 moments at deep and light draughts in certain elementary forms of 

 floating bodies. The proposition I then enunciated, which illustrates 



