The Aerodynamic Research on Windmill Sails of Poul la Cour, 1896–1900 - Wind Power for the World: The Rise of Modern Wind Energy - page 97

Figure 4.3 Drawing of a typical railway station with a Halladay turbine

(above), and photograph from Hjørring railway station in
Denmark (below).

However, it is obvious that la Cour's Askov windmill was of quite
a diferent design compared to what the factory was used to build.
Just to prove that his concept was correct la Cour only needed his
windmill to be as cheap as possible. So he chose the well-known
four-bladed rotor from the standard Dutch windmill design, but