160 ON" THE MOUNTINGS OE THE TELESCOPES AT BIRR CASTLE. 
The Right Ascension circle is represented at Y, and the declination circle is fixed on 
to the axis at Z. 
Plate 11, fig. 4, represents the mounting as seen in a direction parallel to the plane 
of the equator in the meridian and in a direction at right angles to it, the Declination 
axis lying east and west, and the tube directed towards the pole. 
Plate 12, fig. 5, shows the mounting as seen from the west, the tube being directed 
towards a point in the meridian a little north of the zenith. The gallery is shown 
placed in position for observing.* The wall which supports the rail (L), and which 
has two openings, one on the south side to afford a space for the fork to move in, and 
the other at the north side for the admission of the speculum after repolishing, and 
to afford access in working the telescope, has now been omitted from the drawing 
to avoid complexity. 
Plate 13, fig. 6, represents the mounting in plan, the telescope being directed to the 
zenith and the gallery lowered to the ground. 
* There is a slight inaccuracy in the position of the speculum arm in fig. 5. It is screwed on to the 
ring at a point at right angles to that occupied by the eyepiece as in fig. 6, not opposite to the eyepiece. 
