Archaeological investigations of a burned 1916-1919 United States Army  
building at Fort Rosecrans, San Diego, California (CA-SDI-12,000) exposed a  number 
of carbon rods of various sizes. Although some were undoubtedly from  
batteries, other larger ones were associated with search lights used for coast  
artillery sighting. I too have wondered how those were made and how long the  
technology has been around.
 
Ron May
Legacy 106, Inc.