About this there appeared no difficulty, and the result proved there was none; for in less than five minutes after conceiving it, I had carried the design into execution, and the measuring-rod stood inside the barrel, with one end projecting some inches on the outside. Holding this end carefully in my hand, I caused the other to play about on the opposite side, until I felt convinced that it touched the point that was exactly _vis-a-vis_ with the aperture; and then steadying the stick, I notched it with my knife, on a level with the outer surface of the stave. To calculate from this notch would not be correct, as it would be more than the diameter of the cask--that is, in reference to what it would contain--but I had no intention of doing so. I should make allowance for the thickness of the stave, and that would give me the measurement I wanted. Having made my mark, I drew forth my measuring-rod, piece by piece, as it had been plunged in. I took care as I did so to notch both the splices, so that I might be able to put them together again in the exact place where they had been while making the measurement. All this attention to such minute particulars was of importance, and I knew it to be so, for the mistake 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.