In three generations, the Bernoulli family produced 8 mathematicians. 'The Bernoullis and Euler were in fact the leaders above all others who perfected the calculus to the point where quite ordinary men could use it for the discovery of results which the greatest of the Greeks could never have found ... Johannes I did much to spread the calculus in Europe. His range included physics, chemistry, & astronomy in addition to mathematics. On the applied side Johannes I contributed extensively to optics, wrote on the theory of the tides and the mathematical theory of ship sails, and enunciated the principle of virtual displacements in mechanics.' (E.T.Bell, Men of Mathematics (2 vols., 1953), I, p.148)