A Frenchman who arrives in London finds a great shift in scientific opinion that makes the mind weary. He left the world full; he finds it empty. At Paris you see the universe composed of tiny vortices of subtle matter; in London we see nothing of the kind…With the Cartesians, all change is explained by collisions between bodies, which we don’t understand very well; with the Newtonians it is done by an attraction which is even more obscure. In Paris you fancy the earth’s shape like a round melon; at London it is flattened on the two sides.2