Party

SECTION FIRST.

REASONS for fixing on Dunnose and Clifton as the extre

mities of the Arc

General Description of the Zenith Sector

Particular Description of the Zenith Sector

Manner of adjusting the Instrument for Observation

page 5

6

17

Laying off the Points, or dividing the Limb of the Sector
Adjustment of the meridional and horizontal Wires
Particulars relating to the Operations of the Year 1802
Particulars relating to the Measurement of a new Base Line
on Misterton Carr

Angles of the great Triangles observed in the Years 1800,

25

26

28

30

38

1801

40

Reduction of the Base to the Temperature of 62°

44

Recent Comparisons of the standard and working Chains with the Points inserted in the cast Iron Bar

46

Calculation of the Sides of a Series of Triangles
Calculation of the meridional Distance between Dunnose and
Clifton

47

54

Observations made on the Pole Star at Clifton

56

Distance between the Parallels of Latitude of Greenwich and Dunnose

59

(Note) Demonstration of a Formula for finding the Value of Arcs oblique to the Meridian

60

SECTION SECOND.

Operations at the Station on Dunnose, the southern Extremity of the Arc, with the Zenith Sector

Operations at the Station near Clifton, the northern Extremity of the Arc, with the Zenith Sector

Operations at the new Station on Arbury Hill, near Daventry,
with the Zenith Sector

Table, showing the Runs of the Micrometer-screw over
every 5' in the first Degree on each Side of Zero
Table for converting the Divisions on the Micrometer-head
into Seconds

Table for supplying the necessary Correction to the observed
Zenith Distance of a Star on Account of the Expansion
or Contraction of the Axis by 1° of Heat
Reduction of the several Observations made on ß and γ
Draconis, and other Stars, to the first Day of January,
1802

63

71

78

87

88

89

90

100

Deviation of the Cross Wires in the Focus of the Object and
Eye-glasses from the true Line of Collimation
Amplitudes of the celestial Arc, comprehended by the Stations
Dunnose and Clifton

Amplitudes of the celestial Arc, comprehended by the Stations
Dunnose and Arbury Hill

102

103

Difference between the Parallels of Latitude of Dunnose and Greenwich

103

Zenith Distances of y Draconis, reduced to the Beginning of the Year 1794, from Observations made in five successive Years by his Grace the Duke of MARLBOROUGH

106

Subtence in the Heavens of the different Parts of the ter

restrial Arc

page 107

etermination of the Lengths of the Degrees on the Meridian
in the middle Points of the several Arcs
Conclusion

107

109

APPENDIX.

Bearings of the principal Stations in the Counties of Essex,
&c. from the Parallels to the Meridian of Greenwich
Bearings of the secondary Objects

Bearings of the principal Stations of the western Parts of
Kent

Latitudes and Longitudes of the preceding Stations and
Objects

114

117

122

128

PLATES.

General View of the Zenith Sector

No. IX.

Section of the Zenith Sector through the Plane of its Axis
Elevation of the Side of the interior Frame carrying the

X.

Zenith Sector

XI.

Sections and horizontal Views of various Parts of the Sector XII. Elevation of the Plate carrying the Ys, &c.

XIII

In page 19, line 13, for G, read g.

35, lines 5 and 6 from the bottom, for 430 revolutions, read 436.

88, line 3, for 45 divisions, read 4,5.

112, line 28, for 133758 feet, read 802548.

Ib. line 29, for 830196 feet, read 161406.