Dave, I believe the newer edition of Mayall/Mayall covers the Lambert dial. I've been on a campaign to make sure that Foster is given due recognition for having come up with the dial more than a century before Lambert. The dial is usually shown as a horizontal with a movable gnomon at an angle equal to 45 degrees plus half the latitude. The gnomon moves in a slot similar to the analemmatic dial (but different scale). Hour points are equispaced around the circumference.
Some of the discussion noting how the Tercentenary dial can be viewed as a Foster dial appears in my article "Samuel Foster of Gresham College" in the Bulletin of the British Sundial Society, Feb 1997, 97(1):2-15. For a derivation of the Foster dial and a self-orienting variant of it, see my article "A Self-Orienting Equiangular Sundial" in Bulletin of the British Sundial Society, Oct 1991, 91(3):24-25. Fred Sawyer
