I had asked several times about the old formula for Registry Tonnage, & there have been several discussions about it. I ran across the (or a?) formula in "The History and Archeology of Two Civil War Steamboats: the Ironclad Gunboat USS Eastport and the Steamer Ed. F. Dix", prepared for the USA CofE by Coastal Environments Inc. It is stated there that the formula from 1789 until 1864 was (length x 3/5 beam) x (beam x 1/2 depth) divided by 95. " No uniform method for taking the measurements was mandated, such that considerable variations could occur in the tonnages of nearly identical vessels." Based on the tonnage figures I've encountered, considerable variation could also occur when the same vessel was meaured by different inspectors. The source for this formula is given as (Gibson and Gibson 1995a.xxxii) The copy I have does not include the references cited section, so I am unsure of the source refered to.