EARLY ROTATION MACHINERY
The 1847 Plan included weight-driven clockwork mechanisms that turned the whole optic or a part of it, with a stationary lower catadioptric area remaining fixed.
The possibility of rotating external vertical lenses with the main lens remaining stationary was also taken into consideration. In any case, the light patterns attained by these early rotation systems produced rather long-lasting rhythmical patterns.
Two more characteristic of these early rotation systems were the use of galets (small metallic wheels) and the use of flanged speed regulators. Neither should it be forgotten that the weights employed for the rotation of early optical equipment were suspended from a hemp rope (as was the case of Na Pòpia Lighthouse) or an iron chain (at N’Ensiola Lighthouse) and it was not until the beginning of the 20th Century that steel cables and friction-based speed regulators were first introduced.
MERCURY FLOTATION TANKS
With the intention of eliminating the second disadvantage of early rotating optical systems (a long separation between flashes), many of the old catadioptric lenses were adapted to float in tanks of mercury, reducing friction and increasing the speed of optic rotation, to shorten the time between flashes.