1. PICTET'S HIGH SPEED BOAT.
A. Lateral View. B. Plan. C. Section of the boiler room. D. Section of
the cabin.]
Mr. Pictet proposed the problem to himself in a different manner, and as
follows:
Determine by analysis, and verify experimentally, what form of keel will
allow of the quickest and most economical carriage of a given weight of
merchandise on water.
We know that for a given transverse or midship section, the tractive
stress necessary for the progression of the ship is proportional to the
_square_ of the velocity; and the motive power, as a consequence, to the
_cube_ of such velocity.
[Illustration: Fig. 2.--Diagram of tractive stresses at different
speeds.]
The _friction_ of water against the polished surfaces of the vessel's
sides has not as yet been directly measured, but some indirect
experiments permit us to consider the resistances due thereto as small.
The entire power expended for the progress of the vessel is, then,
utilized solely in displacing certain masses of water and in giving them
a certain amount of acceleration. The masses of water set in motion
depend upon the surface submerged, and their acceleration depends upon
the speed of the vessel.
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