[4] It seems that the lighthouse erected by Sir John consisted merely of a house built with timber lath and plaster on the top of which a light was kept in a large glass lantern for the purpose of directing ships in their course.

But near the end of the same century a strong octagonal structure of flint was erected on the top of which was an iron grate quite open to the air in which a good fire of coals was kept blazing at night.

[5] About the year 1732 the top of this lighthouse was covered with a sort of lantern with large sash windows, and the fire was kept bright by bellows with which the attendants blew throughout the night.

Complaints of this sort were so loud and frequent that the governors of Greenwich Hospital sent Sir John Thomson to examine and make arrangements on the subject.

In 1792, under the supervision of John Yenn (Surveyor to Greenwich Hospital), two stories of brick were built on the original structure which raised it to the height of 100 feet including the lantern room at the top in which the lights were kept.

)[4] At the same time oil lamps were installed in the tower, together with a new optical system designed by Thomas Rogers (who had previously installed a similar system in the lower lighthouse at Portland): it consisted of two rows of nine lamps and reflectors arranged in a convex curve,[6] placed behind a row of solid glass convex lenses which were incorporated within the glazing around the lantern room.

[7] In it, under the supervision of engineer Henry Norris, a new multi-wick oil burner was installed together with a large (first-order) fixed catadioptric optic manufactured by Sautter & Co. of Paris (replacing the previous catoptric apparatus of 18 Argand lamps & reflectors); it was first lit on 26 March 1860.

[8] Three months later a red sector was added to the light, which shone northwards 'to enable vessels at night to keep to the eastward of Margate Sand'.

[9] (These works coincided with the successful experiments carried out in 1857–60 at the South Foreland lighthouse by Professor Frederick Hale Holmes with an alternating current electric arc light).

[5] An inner circular brick wall was then constructed, which supported a new cantilevered stone staircase leading from ground level to the service room, immediately below the lantern.