444 
ME. E. J. EEED ON THE UNEQUAL DISTEIBUTION OE 
importance of careful stowage must be fully realized, as well as the connexion which 
should subsist between the ship’s form and the distribution of her weights. Some 
existing views have been shown to be erroneous, — notably those respecting the effect of 
an excess of weight amidships, and the position of the section of maximum strain. The 
classification I have adopted for ships is confessedly imperfect ; but no general laws 
can possibly be laid down to include the very varied characters of the distribution of 
weight and buoyancy in all ships, and the types I have chosen have at least the merit of 
including a very large proportion of the cases met with, besides permitting a generality 
of investigation such as has not been previously attempted. 
In attempting to approximate to the shearing- and bending-strains of ships at sea , we 
meet with a problem of great difficulty, and one which in the present state of our know- 
ledge does not admit of complete or exact solution ; in fact it may be doubted whether 
the very varied and rapidly changing conditions of strain in ships so situated will ever be 
completely expressed in mathematical language, and brought within the range of accu- 
rate calculation, in the same way as still-water strains have here been treated. It is, 
however, possible to distinguish the principal causes of straining in ships at sea, and 
in some cases to make approximations to what may be considered as their limiting 
values, as I shall show further on ; but the dynamical aspect of the question, although 
the most important of all, is at present in some respects beyond our power, so far as its 
expression in quantitative form is concerned. That this is the case will be obvious on 
the most cursory glance at the condition of a ship in a sea-way. Neglecting, for the 
sake of simplicity, all consideration of rolling motion, and supposing the ship to lie 
directly bow on to the waves, the passage of each wave along her length establishes, or 
tends to establish, a vertical motion in the ship as a whole (except under certain special 
conditions), and a rotatory or pitching motion about some transverse axis, besides pro- 
ducing continual changes in the relative distribution of the weight and buoyancy all 
along the length. The ship’s motion in pitching and ascending can be readily explained 
in general terms ; but to express accurately the speed of that motion, and the corre- 
sponding accelerating forces, as well as the straining effect of the percussive shocks that 
are nearly certain to be caused by it, is an undertaking 1 shall not attempt. Even if 
this could be done, it would still be necessary to consider the heaving or vertical motion 
of the ship and the rapidly varying nature of the wave supports, both of which are 
causes of important straining-actions ; and, in addition, to deal with the effect of the 
passage of a succession of waves (far from being of uniform dimensions and periods) 
as well as with the influence of the ship’s onward motion. Altogether, therefore, we 
have before us a most complex question, which can only be touched, as it were, by some 
approximative method such as that I am about to describe. 
From what has just been said, it will appear that there are three principal causes of 
increase in the longitudinal strains of ships at sea, as compared with their still-water 
strains, — the vertical or heaving motion of the ship as a whole, which is nearly sure to 
result from the wave motion, because ships share to some extent the motion of the waves ; 
