Illustration of the Vortical Theory by Rene Descartes from Principiae Philosphiae,part 4,The Earth,published in 1644. This is a vortical explanation of the Earth's magnetic field. In the top illustraton the Earth is represented by the letters A,B,C & D,with the south pole placed at A and the north at B. The smaller circles (N,M,L,K & I) correspond to the magentic field on a compass as it would effect the Earth from the different positions. The screw shaped particles,which correspond to the magnetic lines of force,travel in a vortical motion through pores in the Earth's surface. The lower image is an explanation of the attraction of magnetic opposite poles |