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A statute of 1765 confirmed the right of supervision vested in theroyal society and exercised by the board of visitors. In 1770 two re-volving domes were constructed upon the turrets, and these have servedas models for all revolving turrets since constructed. In 1772 the firstachromatic object glass ever used at Greenwich was attached to the southquadrant. In 1779 the expediency of enlarging the meridian openingswas acknowledged; hitherto the aperture had only been 6 inches(0.15 m ).
At the beginning of the present century it became necessary to re-build the observatory, and the work, continuing until 1811, consisted inthe construction of two rectangular buildings, the eastern one being theobservatory proper, and containing halls for the meridian instruments,the library, and office, while the western structure was intended for thedwelling house of the superintendent.
The present organization of Greenwich Observatory daces from aroyal statute of 1830. According to the terms of this statute the boardof visitors consists of the members of the Royal Society , the membersof the Astronomical Society, and the Oxford and Cambridge professorsof astronomy.
As a finishing touch the immense dome to the southeast was built in1859.
Instruments :
(a) Meridian circle: One; makers, RANSOMES & May (engineers),Troughton & Simms (opticians); diameter of circle, 72 inches; dividedto 5'; read by six microscopes to 0.06"; four supplementary microscopesfor determination of division errors and occasional use: aperture of ob-jective, 8.1 iuches ; for observations of the sun, aperture employed, 8.1;magnifying power ordinarily employed, 195 diameters.
(b') Alt azimuth: Makers, Ransomes & May and W. Simms; aperture,4 inches. Magnifying pow r er, 100; diameter of circles, 3 feet, dividedto 5'.
(c) Equatorial instruments ; Makers, Ransomes & Simms (engineers),Troughton & Simms (opticians), Merz (objective); aperture of ob-jective, 12.8 inches; magnifying power of .eye-pieces, 60 to 1500. (&)Sit caps hank's equatorial: makers, T. Grubb, Cauchoix (objective);aperture of objective, 6f inches. Naylor equatorial: maker, T. Cooke,of York; aperture, 6 inches. Shuelcburgh equatorial: maker, Ramsden;aperture, 4.1 inches.
(d) Spectroscopes: Half-prism spectroscope; maker, IIilger. Directvision: one, two, or three compound “ half-prisms ” with dispersions (Ato H) of about 18J°, 83°, and 335°. Single prism stereoscope: Makers,Troughton & Simms ; one flint prism.
(e) Photometer : Airy’s double-image micrometer; makers, Trough-ton & Simms.
(/) Chronograph: Makers, E. Dent & Co.