But it would be necessary, as has been proved by several people, and even by those who are of this opinion and wish to support it, it would be necessary, I say, for this matter to revolve about seventeen times faster than the earth without changing the perpendicular direction of a falling feather, and without offering the least resistance to a man walking in the opposite direction of its motion, although it offers a great deal of resistance to our effort to raise ourselves from the earth, which seems to contain a manifest contradiction.