Five-feet Equatorial Instrument. 5 
the axis are supported on stones ; the northern one rising 
within about four inches of the level of the axis of the decli- 
nation circle ; the rest of the support being of wrought iron. 
At the southern end the stone rises very little above the floor, 
but a cast iron frame supports the pivot at the height of about 
two feet. The Y, or angle which receives the lower pivot, 
is placed upon the frame, and provided with two screw adjust- 
ments, one for giving the axis its due elevation, and the other 
for bringing the instrument to the meridian. The form of 
the iron-work above-mentioned will be sufficiently compre- 
hended on consulting the different figures of the Plates. 
The two branches of the polar axis, on their upper sides, 
are formed of broad planes, both making one continued plane. 
On these surfaces the axis and reading microscopes of the 
declination circle are fixed. The plane is as much above the 
line of centre as was judged would render the instrument 
self-balanced ; but the declination circle, &c. having proved 
somewhat lighter than was expected, an equilibrium is ef- 
fected by a weight fixed to the conical part of the polar axis. 
The diameter of the declination circle is four feet, the length 
of the telescope five feet, and the axis about thirty-two inches 
long. In Plate I, fig. 1, the declination circle appears quite 
plane, exhibiting the form of a drum-head, with the telescope 
looking towards the equator, and projecting at each end a little 
beyond the circle. In Plate II, the draughtsman stood close 
to the south pole of the instrument, on account of which, and 
its elevation, the polar axis is considerably foreshortened. 
In this figure the edge of the declination circle is shown as a 
short cylinder, the object-end of the telescope protruding 
beyond it. In this figure is also seen the shape of the 
