the salmon (Fig.nb13) may be cited as typically fish-shaped fish.
Beyond the lessons to be derived from these natural forms, there is very little practical information available. The lines of ships are governed by considerations foreign to the subject, the question of wave-making, for example, being a matter of vital importance. The submarine has not yet reached a stage of development that would justify its form being taken as a fully
Fig. 14.
evolved model; also, for obvious reasons, this type of vessel is one of which but little information has been published.
In Figs. 11 and 12 curves are given whose ordinates represent the area of cross-section at different points. This curve has been obtained by differentiating a displacement curve plotted from a series of immersion measurements. These measurements were made by a method of displacement, the fish, suspended tail downward, being lowered stage by stage into a vessel of water, measurements being made of the overflow.
The area curves have been further translated into the form of
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