Figure I. is a section of the instrument formed of mahogany or boxwood. A A are two oblong square cavities connected together by a narrow close channel, running from the bottom of the one to the other. B B are two grooves hollowed out of the wood, in order to contain the fights, &c. They are shut up by a lid, which turns upon a screw-nail at the centre C, as may be seen more distinctly from fig. 4.