WEIGHT AND SUPPORT IN SHIPS. 
415 
water on the immersed part of a ship. Euler seems to consider that it will tend to 
reduce hogging ; the reverse is really true, as we shall see hereafter. In his later work 
(the ‘ Theorie complette ’) Euler omits all consideration of the effect of this pressure. 
No quantitative or practical results are arrived at in this division of Euler’s work. 
In Don Juan’s celebrated ‘Examen Maritime’ (1771), the graphical method of inves- 
tigating the forces which result from the varying distribution of weight and buoyancy 
is again adopted, and the author attempts to make an approximation to the magnitude 
of the resulting bending-moments. He assumes that the immersed part of a ship may 
be represented by two surfaces of revolution, the fore body being generated “ by the 
revolution of a semiellipse, and the after body by the revolution of a parabola,” about 
a common axis coinciding with the middle line of the section made by the plane of 
floatation. No practical importance attaches to his results, since they rest upon so many 
assumptions ; but the work is interesting on account of the grasp of the general condi- 
tions of the problem which Don Juan displays. 
Romme, in ‘ L’art de la Marine’ (1787), gives some attention to this subject, in the 
main following Bouguer ; but the chief interest of his observation lies in the informa- 
tion which he gives respecting the extent to which the ships of his day yielded to the 
bending-strains, and the practical methods resorted to for mitigating the evil. 
This rapid glance at what the earlier writers had to say upon the subject brings us 
down to the present century, when our own countrymen took it up. Sir Robert Seppings 
was the first who applied himself to it, but he did little or nothing to advance the science 
of the question. Dr. Young was, however, fortunately called upon to report on Seppings’s 
practical improvements, and brought great ability to bear upon the whole subject of the 
strains of ships, giving the valuable results of his investigations, first in a Report to the 
Admiralty (1811), and afterwards in a paper submitted to the Royal Society, and pub- 
lished in its Transactions (1814). A perusal of Dr. Young’s paper clearly shows how 
very necessary it is, in discussing this subject, to place one’s self in possession of such 
detailed calculations as I have now had carried out for several typical ships, the results 
of which I shall presently place on record. The “ causes of arching ” are first considered, 
the unequal distribution of weight and buoyancy being assigned as the chief cause, and 
hogging being named as the ordinary effect, although Dr. Young thinks that there are 
many cases “ in which a strain of a very different kind is produced.” Alterations in stowage 
are also mentioned as causes of variation in the strains. As a type of ordinary ships, 
an English 74-gun ship is taken, for which the details of weight and buoyancy had been 
calculated for various parts of the length. Dr. Young makes various arbitrary assumptions 
with respect to the positions of the centres of action of the resultant vertical forces of 
which he thus knows the amounts, and by this means obtains a balance of the moments 
of the upward and downward forces about either end of the ship, which is obviously 
necessary in order to satisfy the hydrostatical conditions of equilibrium for the ship.. 
The result at which he arrives is graphically represented. Dr. Young indicates a correct 
method of calculating the bending-moments at various parts of the ship, and makes an 
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