Footnote 5
Part I, §3.  The Moder.  In Latin, Mater or Rotula.  This forms the body of the instrument, the back of which is shewn in fig. 1, the front in fig. 2.  The `large hole' is the wide depression sunk in the front of it, into which the various discs are dropped.  In the figure, the `Rete' is shewn fitted into it.