istake of even a quarter of an inch in the length of my
diameter would cause a difference of many gallons in the result. Most
certainly, then, was it of consequence that I should be precise in my
_data_.

I now had the diameter of the swell; the next thing was to get that of
the head, or end. About this there was less difficulty--in fact, not
any. It was obtained in a few seconds.

Though I could not myself get round either of the ends of the butt, nor
even my arm, I could pass the rod around them, and in this way measure
them. Even had there not been space to admit the measuring-stick, I
should have found a means--by simply drilling another hole with my
knife, close to either end, and gauging as before. But this would have
occupied time, and it was not necessary to do so, since the stick passed
along the head of the butt without any obstruction, till its end rested
against the projecting rim on the opposite side. I had nothing to do
but assure myself that its point was fair in the middle, and then make
my mark as before.

The length of the butt was yet to be ascertained; and this, though
apparently a simple operation, cost me a good deal of consideration,
before I could get at it with any degree of exactness. You may fancy
that it would have been easy enough to get at the length, by just
placing the stick parallel to the cask, and notching it square with the
ends of the latter? And so it might be easy enough, with plenty of
light around you to see when it _was_ square, and a level surface upon
which to rest your measure. But as I had the advantage neither of light
nor level ground, I encountered great difficulty in this operation. I
could not tell when the ends lay even with each other, merely by the
touch. I had to pass my fingers from one to the other, and could not
grasp both at one time--that is, the rim of the cask and the end of the
rod--since they must needs be several inches apart. The stick, too, lay
unsteady, and by the feel I could not be sure when its end was exactly
"flush" with the head of the cask. The mistake of an inch--it might be
several--would falsify all my computations, and render them of no use.
It would not do to proceed upon such a conjectural basis, and for a
while I was puzzled, and had to pause.

This was an unexpected obstacle, for I had from the first regarded the
diameters as the only difficulty; about the possibility of obtaining the
length, I had never entertained a dou