19 assemblies comprising the jointed arms for the peep-sight of the Perspective Instrument. The arm to be fixed to the case is a straight bar of mahogany, of rectangular cross-section, with the ends guarded with brass like those of a wooden rule, each drilled with a hole. The other piece. also of mahogany, is lighter and of a tee section. The two are jointed by a brass elbow-fitting. The free end of the lighter bar is fitted with a brass guard that also forms a socket for the sight vane, a leaf-shaped piece of brass with a pin to fir the socket. Each has two peep holes, of different sizes, and a small piece swinging on a rivet to cover whichever hole is not in use. One assembly lacks the sight vane [but there is one in the tall cabinet!]. Nineteen assemblies comprising the jointed arms for the peep-sight of the Perspective Instrument 1790-1819