Ormewood is correct that later revisions by someone to put all wind considerations into one section caused a loss of continuity I was the original author of the section Shape of The Tower in March of 2007 so I know that the orphaned sentences answer the question What mathmatical calculation was Eiffel referring to I tried to edit the article but found it is now semi protected owing to excessive vandalism I propose that an autoconfirmed user revise the entire paragraph as follows In search of what mathmatical calculation Eiffel referred to researchers have found that Eiffel used empirical and graphical methods accounting for the effects of wind rather than a specific mathmatical formula Careful examination of the tower shows a basically exponential shape actually two different exponentials the lower section overdesigned to ensure resistance to wind forces Several mathmatical explanations have been proposed over the years the most recent is described as a nonlinear integral equation based on counterbalancing the wind pressure on any point on the tower with the tension between the construction elements at that point As a demonstration of the tower s effectiveness in wind resistance it sways only 6 7 cm 2 3 in in the wind I would be happy for any assistance in further editing or rewriting