370 1 2 Schmidl, Petra G. (2014-05-08), "Compass", in Ibrahim Kalin, The Oxford Encyclopedia of Philosophy, Science, and Technology in Islam, Oxford University Press, pp. 144–6, ISBN 978-0-19-981257-8 ↑ The magnetic lines of force in the Earth's field do not accurately follow great circles around the planet, passing exactly over the magnetic poles.