J. Campbell's Astronomical Observatory. 67 
The handle and also the operator move round with the dome, 
which is accomplished in a very convenient manner, by the pecu- 
liar construction of the observer’s seat. This is a small flight of 
a : 
Endless screw and pinion on the horizon for moving the door of the aperture. 
Stairs, at an angle of elevation, suited to the sweep of the eye- 
piece, so that each step makes a convenient seat. Fig. 8 h 
frame is of wrought iron—the string pieces reach to the base of 
the dome, to which they are secured, as seen in the plans., The 
bottom of the stairs rests upon two wheels, in which grooves 
are made to suit a circular rail of half round iron, which is 
the bottom steps of the observer’s seat, and consequently revolv 
With it, see figs. 2 and 3. It will be perceived that by this ar- 
d the reading table 
rangement the aperture, the observer's See y involves the 
are so constructed that the moving of one 
