348 Mr. mudge on the ConJlruBion 
produces the moft beautiful polifh ; and by its pliability 
is better calculated for that mutual accommodation be- 
tween polifher and metal,, fo neceffary to the figure pro- 
pofed. 
EXPLANATION OF THE FIGURES. 
Fig. i . The grinder for working off the rough face of 
the metal; the black ftrokes reprefent deep grooves 
made with a graver. 
Fig. 2. The bed of hones, which is to complete the 
fpherical figure of the fpeculum, and to render its 
furface fit for the polifher. 
Fig. 3. An apparatus for examining the parabolic figure 
of the fpeculum. 
a a The mouth of the telefcope, or edge of the great 
tube. 
bb„ A thin piece of wood fattened into, , and flufh with the 
end of the tube ; to which- is permanently fixed the 
annular piece of pafte-board ce, intended to cover, 
and to prevent the action of the correfponding part 
of the fpeculum. 
r>. Ano- 
