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Situations of the stations

TRIGONOMETRICAL SURVEY, 1795, 1796.

Principal angles observed in 1795

Iron cannon inserted at the extremities of the base on Salisbury
Plain

Principal angles observed in 1796

Calculation of the sides of the principal triangles, extending to

the Land's End

Observed elevations and depressions

Terrestrial refractions: and heights of the stations

Height of the station on Maker Heights found by levelling
Secondary Triangles.

360

862

365

870

372

377

383

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Situation of the Eddystone Light-house determined

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of the Lizard Light-houses

403

of the Scilly Light-house, and other objects in the Scilly

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411, 418, 421, 423

Principal and secondary triangles

Bearings and distances from the meridian of Greenwich and its perpendicular

Latitudes and longitudes of the intersected objects in Kent

4.12 to 427

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PLATES.

Plan shewing the situation of the base on Hounslow Heath

Steel chain

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Deal rods

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XII.

XIII.

Glass rods

Pyrometer

Apparatus for the measurement on Romney Marsh

Plan shewing the situation of the base on Romney Marsh
General view of the circular instrument

Plan and two sections of ditto

Various parts of ditto

Microscopes and eye-pieces

Articles of machinery used in the operation in 1787, 1788
Positions of the stations on the tops of towers, &c.

Plan of the triangles connecting the meridians of Greenwich and
Paris

Geometrical diagrams

For improving the map of London, &c.

Transit instrument

Plank and bar used in measuring the chains

XIV.

XV.

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XIX.

Handle of the chain. And geometrical diagrams

Plan of the principal triangles in the Trig. Survey, 1791–1794 xx. in the Trig. Survey, 1795, 1796 xxi.

Part of Kent and Sussex

XXII.

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AN ACCOUNT, &c.
By William Roy.

INTRODUCTION.

ACCURATE surveys of a country are universally admitted to be works of great public utility, as affording the surest foundation for almost every kind of internal improvement in time of peace, and the best means of forming judicious plans of defence against the invasions of an enemy in time of war; in which last circumstances their importance usually becomes the most apparent. Hence it happens, that if a country has not actually been surveyed, or is but little known, a state of warfare generally produces the first improvements in its geography: for in the various movements of armies in the field, especially if the theatre of war be extensive, each individual officer has repeated opportunities of contributing, according to his situation, more or less towards its perfection; and these observations being ultimately collected, a map is sent forth' into the world, considerably improved indeed, but which, being still defective, points out the necessity of something more accurate being undertaken, when times and circumstances may favour the design.

The rise and progress of the rebellion which broke out in the Highlands of Scotland in 1745, and which was finally suppressed, by his Royal Highness the late Duke of Cumberland, at the battle

B

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