It is difficult to
judge exactly of these matters. Some four years ago the Italian
government adopted treble bottoms for their heaviest ships as a result
of experiments with seventy-five pounds of gun-cotton (the charge of
an ordinary Whitehead locomotive torpedo) against a caisson which was
a _fac-simile_ of a portion of the proposed ships. Only two of the
bottoms were broken through, and when the space between the two inner
bottoms was filled with coal, only the outer bottom was broken.
According to the formulae of either Abbot or Bucknill, there should
have been a local pressure of at least 300,000 pounds per square inch
on the outer skin, and yet judicious interior arrangements rendered it
harmless to the target. It would not, however, be safe to conclude
that the torpedo was thus vanquished; the immediate result was simply
to create a demand for larger locomotive torpedoes for local
application, and but little light was thrown upon the results which
might be anticipated from a large mine at a greater distance, whose
radius of explosive effect would embrace a larger portion of the ship,
and especially if the ship were nearly over the torpedo.
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