Mercury floats for revolving lenses by Kraig Anderson and Jim Woodward

This table is a compilation of information culled primarily from the Inspection Reports available from the National Archives for lighthouses where a mercury float was used along with a clockwork mechanism to revolve a lens. The table includes the following categories of information: Lighthouse name; Year of report (or other source of information); Order of lens;  Lens manufacturer; Mercury float manufacturer; Pounds of weight used for powering the clockwork mechanism; Time of one revolution; Length of Drop Tube (if any); and Time between windings. In many of the reports, data was simply not included for all of the categories, but the extracted information nonetheless gives a heretofore underappreciated glimpse into this aspect of lighthouse operation.

For manufacturers:  BB = Barbier & Benard, BBT = Barbier, Benard, et Turenne, C = Chance Brothers, FB = F. Barbier & Cie, HL = Henry-Lepaute, LS = Louis Sautter, ME = Macbeth-Evans, and USLHS = U.S. Lighthouse Service

Please note this list is not complete as it is based primarily on available Inspection Reports, which do not cover all lighthouses and time periods. There is some evidence the following lighthouses also used a mercury float at some point but more documentation is needed before they can be added to the official list: New London Ledge CT, Saybrook Breakwater CT, Robbins Reef NY, and Block Island North RI. The following lighthouses appear on a list of lenses with a Mercury Float that were purchased from Barbier, Benard, et Turenne: Bellevue DE, Cape San Blas FL, Crescent City CA, Eldred Rock AK, Gasparilla FL, Horseshoe Reef NY, Marblehead MA, Mukilteo WA, Race Rock NY.