A process had been discovered in the 1770s whereby additional quantities of lead could be extracted from the fumes emitted by reverberatory furnaces if the vapours could be trapped long enough to precipitate the lead. To this end a flue long running from the lead works and terminating at a chimney near the summit of Carrickgollogan was constructed in 1836. The precipitated lead deposits were scraped out of the flue by hand and many of the workers subsequently died of lead poisoning, giving the surrounding area the nickname Death Valley. The distinctive granite flue chimney with its external spiral staircase and viewing platform quickly became a noted landmark and was marked on Admiralty charts as a point of reference for mariners. Photographic records show that the flue chimney was originally much taller with an extra brick section, now dismantled, rising above the viewing platform. It is the only example of such a flue and chimney to have been built in Ireland. Weston St. John Joyce noted that the flue was stated to be one of the best constructed in the United Kingdom.