ballast
Isaac Kremer/ January 14, 2018/ / 0 comments
The filling of rough masonry required to give stability and weight to any construction, as above the haunches of light vaulting, also the rough broken stone or gravel used as such filling. 2. A device for maintaining the current through a fluorescent or HID lamp at the desired constant value, and sometimes also providing the required starting voltage and current. (Sturgis, 1900)