When Laplace studied the tides he had ignored fluid friction because no good mathematical treatment existed at that time. However Navier, Stokes, Poisson and Saint-Venant had developed a mathematical theory of fluid friction in the 1840s. Airy had assumed that the friction was proportional to the velocity and had developed results based on that assumption in 1845. However this assumption is not realistic, but the realistic assumption that the friction is proportional to the square of the velocity produced non-linear equations which were much more difficult to treat. Ferrel became the first to treat the non-linear case successfully.
Kapag nag-aral ng Laplace ang tides niya pinansin likido salungatan dahil hindi magandang matematiko paggamot nabuhay sa oras na iyon. Subalit Navier, Stokes, Poisson at Saint-Venant ay binuo ng isang matematiko teorya ng likido sigalot sa 1840s. Airy had assumed na ang mga alitan ay nauukol sa bilis at nagkaroon na binuo batay sa mga resulta na palagay sa 1845. Subalit ito palagay ay hindi totoo, ngunit ang talagang palagay na ang mga alitan ay nauukol sa square ng tulin produced non-guhit equation na kung saan ay mas mahirap na gamutin. Ferrel ang naging unang sa paggamot ng hindi-haba kaso matagumpay.