Early form of theatrical lighting. The incandescent calcium light invented by Thomas Drummond in 1816 was first employed in a theatre in 1837 and was widely used by the 1860s. Its soft, brilliant light enabled it to be focused for spotlighting and to create effects such as sunlight and moonlight. The expression in the limelight referred to the most desirable acting area on the stage, the front and centre, which was illuminated by limelights. Electric lighting replaced limelight in the late 19th century.