bt.

But my wits again came to the rescue, and I soon discovered a plan that
would effect the end in view. I had to make another rod--by splicing
two more lengths split from the board--and with this I was able to
determine the point.

I managed the matter thus: The old rod I pushed along the head of the
cask quite beyond its outer edge, so that it rested at both ends against
the projecting rim. Thus placed, it was exactly parallel with the plane
of the barrel's head, while a foot or more projected outward and towards
me. Holding the end of the second rod against this projecting part, and
at right angles, I gave it a direction along the side of the cask, and I
was able to mark the point, where the middle part of the swell came in
contact with the second rod. This, of course, after deducting the depth
of the rim and the presumed thickness of the head, gave me half the
length of the interior of the cask, and that was all I wanted, since two
halves make one whole.

I was now in possession of the _data_ of my problem; it only remained
for me to seek the solution.

CHAPTER THIRTY ONE.

"QUOD ERAT FACIENDUM."

To find the cubic contents of the butt in feet or inches, and afterwards
reduce them to liquid measure--to gallons or quarts--would have been
easy enough, and only required a simple computation in figures. I knew
that I was arithmetician enough to make this computation, even though I
possessed neither pen nor paper, slate nor pencil; and if I had, there
was no light by which I could have used them. "Ciphering," therefore,
in the ordinary way, was out of the question; but I had often practised
myself in casting up accounts by a mental process, and I could add and
subtract, multiply or divide a considerable series of figures without
the aid of either pen or pencil. The problem I had before me would
involve but a limited number of figures, and I felt satisfied I could
easily manage it, so far as that was concerned.

I have said that it _would have been_ a simple and easy computation to
find the contents of the cask in cubic feet or inches. _Would have
been_ supposes that there was a difficulty--and there _was_ one. An
important preliminary matter had to be settled before I could enter upon
any calculation--a very important one; and that was, that I had not yet
reduced my measurements--neither the diameters nor the length--to feet
and inches! I had measured the cask with plain pieces of stick, and had