Traditional wisdom considered the action of wind on the wings as an impulse of particles, which made Newtonian calculations possible. Although Daniel Bernoulli and Leonhard Euler had laid the foundation of modern fluid dynamics a hundred years earlier this had had no consequence for such complicated practical problems as that of the action of wind on wings; and in the cases where a computation was possible, theory did not match experience (Paradox of d'Alembert). The union of theory and experiment came mainly through careful wind tunnel experiments. The Danish tradition in this area was started by H. C. Vogt and Johan Irminger in the early 1890s. La Cour continued in 1896 when he started to test small models of windmills in a wind tunnel, probably the first such experiments in the world focusing on windmills.