The cross section drawing (fig. 4) shows the 9/16" thick bottom and the sides which are 1/8" thick. The lining, 1/2" by 1-1/3", runs around four sides of the instrument, the wrest plank replacing it on the fifth side. The soundboard thickness, measured inside the holes through which the jacks pass, varies from 1/16" in the bass to 1/8" in the treble. The manner in which variations in thickness are distributed over the entire soundboard has not been determined. The cross section drawing also shows the beautifully executed mouldings that make the sides appear to be thicker than they really are. The positions of the knee braces, the shape of which can be seen in figure 4, are shown along either side of the keyboard in figure 5. These braces are 3/4" thick. The positions of the blocks, small pieces with the grain running perpendicular to the bottom, and the wrest plank, which is 1-1/4" thick, are also shown. The two ribs are attached to the underside of the soundboard in the positions indicated. The jack guide, built up of separate pieces held together by long strips down either side, is glued to the underside of the soundboard and extends as far as the lining in the treble but stops a little short of it in the bass (fig. 5). The jack guide is 15/16" thick. The layout of the soundboard in figure 6 gives the relative positions of the bridges, tuning pins, hitch pins, strings, jacks, and jack rail. There is, of course, one jack and one string per key. The jacks presently in this virginal, not being original, will not be described. Typical Italian jacks will be described later. The bridges are 5/16" wide and vary in height from 7/16" in the bass to 3/8" in the treble. A cross section of one of the bridges appears in figure 4. The jack rail, also shown in figure 4, extends over the jacks 1-1/8" above the soundboard. It serves not only to prevent the jacks from flying out during play but also to terminate the downward fall of the fronts of the keys. The keys do not drop far enough to touch the key frame, but instead are stopped by the jacks striking the jack rail. [Illustration: Figure 4.--CROSS SECTION OF POLYGONAL VIRGINAL. A, side; B, bottom; C, knee; D, liner; E, soundboard; F, rib; G, bridge; H string; I, jack rail. Scale, 1:2.] The keyboard has an apparent compass of four octaves and one note from _E_ to _f'''_. Short octave tuning would have extended the compass down a major third to _C_ in the bass, with the _E_ key sounding _C_, the _F#_ key sounding _D_, the _G#_ key sounding _E_, and the remaining keys sounding their proper pitches. These three keys will hereafter be referred to as _C/E_, _D/F#_ and _E/G#_. The lowest eight keys have small wire eyes attached to their undersides near the front. A corresponding slot is cut through the inner and outer cases, allowing the eyes to be connected to a short pedal keyboard which has not survived.