194 OBSERVATORY AT WEST POINT. 
silver sunk into its outer surface, which is twelve inches in diameter, and reads, by the 
aid of three verniers, to a second of time. 
Upon the square flanch, at the top of the polar axis, rests a cast iron frame for support- 
ing the declination axis. It consists of a cubical base eight and a half inches on the 
edge, perforated on opposite faces with which are united at their larger bases two short 
hollow conic frustrums (16). Attached to one end of this frame is a circular flanch (17), 
fifteen inches in diameter, with a channel in its circumference to receive a friction hoop 
for the tangent screw (22), Fig. S, of the telescope and declination circle. 'T'wo pieces 
of Brazilian metal, similar to those shown in Fig. C, are let into the concave surface of 
the opening in this circular flanch, and serve as Y bearings for one end of the declination 
axis. ‘The other end of the frame terminates in a short flanch against which is sup- 
ported, by strong screws, a circular plate (19), of Brazilian metal. This plate has a cir- 
cular apperture large enough to receive freely the declination axis; and to secure the 
proper bearing points, the lower edge of the aperture is cut away, as shown at (20), Fig. 
D, thus converting the circular into a Y bearing for the other end of the axis. The screw 
holes in this plate are of an oblong shape, to admit of a motion in the plate itself in the 
direction of the polar axis. This motion is communicated by means of a device, shown 
at (21). By this, the declination axis is adjusted. ; 
This axis (23) is represented out of its bearings, because the section is made where 
they are not found. One end of this axis has a strong square flanch eight inches on a 
side, and to this the cradle of the telescope is attached by strong screw bolts, of which 
the head of one is seen at (26), Fig. S. The diameter of this axis at the bearing surface 
nearest the telescope is four inches, and at the other, a little more than three. About 
three-fourths of an inch from the bearing plate (19), the axis is contracted to form a 
shoulder to receive the declination circle (24), which is secured by two strong steel 
screws; and beyond this, the axis projects about eleven inches to receive the counterpoise 
weights (27). To prevent all motion in this axis in the direction of its length, a steel 
roller (34), about one inch in diameter, and twenty-eight inches long, is held in the centre 
of the polar axis by two perforated steel bars (35), (36), which are firmly attached to the 
polar axis, and within which the roller turns with the utmost freedom, but without play. 
At the upper end of the roller is a circular head, whose diameter is just equal to the 
width of an annular groove in the declination axis within which it works. The axis is 
pressed into its bearings by a friction wheel which enters the cubical box at the top, and 
is secured in its place by a stiff frame and screw (29); and the whole frame is securely 
attached to the head of the polar axis by strong screw bolts (30), represented in dotted 
lines. 
The declination circle (24), which is fifteen inches in diameter, is also of brass, and the 
graduation is on a band of silver sunk into its outer rim. It has two verniers (32), 180° 
apart, by which the smallest count is fifteen seconds of space, and two reading micro- 
meters (31), by which the smallest count is reduced to one second. 
The clock-work is represented at (37), Fig. S. It is put in communication with the 
instrument by means of a circular sector (38), whose centre of curvature is in the polar 
axis, and whose circumference is provided with teeth that work into an endless screw, of 
which the axis is seen at (48). ‘To the arm (40) of this sector, one of the nuts (41) of the 
