as may appear in the Philosophical Transactions relating to the Trigonometrical Survey, will, from time to time, be republished by himself. He has, therefore, denominated this, the First Volume.

WILLIAM MUDGE.

ISAAC DALBY.

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

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,

1801

Reduction of the Base to the Temperature of 62°

Recent Comparisons of the standard and working Chains

with the Points inserted in the cast Iron Bar

page 5

6

17

25

26

28

30

38

44

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

[iv]

SECTION SECOND.

Operations at the Station on Dunnose, the southern Extre-

mity of the Arc, with the Zenith Sector

Operations at the Station near Clifton, the northern Ex-

tremity of the Arc, with the Zenith Sector

Operations at the new Station on Arbury Hill, near Daventry,

with the Zenith Sector

63

71

78

-

87

88

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

-

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

[v]

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

[vi]

PLATES.

General View of the Zenith Sector

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

No. IX.

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.