Sometime in the early 1820s, Michael Faraday
performed a demonstration at the Royal Institute of London where he turned an oxygen
flame on a lump of quicklime. The light that was emitted from the lime was brilliant. How brilliant? Lt. Thomas Drummond, in the audience, applied what he had seen to his surveying
techniques. In 1825
, Drummond set a limelight marker on a mountaintop
. It was so bright it could be seen in Donegal
county (sixty-six miles away).
By 1837, limelight lanterns were streamlined enough that they made their way into the theatre. English theaters at that time were being lit with coal gas (an exciting technological improvement over the candles and lanterns). Limelight brought the brilliance of the noon day sun into the theatre, where it could be dimmed or colored to soften it as needed. One downside (apart from the tricky business of controlling the flow of hydrogen and oxygen) was that light operators would have to replace the cylinders of lime over the course of the play. Electric lights eventually replaced the limelights. The phrase "to be in the limelight," refers to the attention one would receive as a follow spot directs this bright light on you.
Limelight also found its way onboard ships and in lighthouses, for communication; into construction, so that in the Civil War, for example, the the Union Navy could see Fort Sumter as they pounded it into rubble.
Source: Dr. John H. Lienhard, Engines of Our Ingenuity