Making a magnet by hammering. Illustration from the book De Magnete by William Gilbert of 1600. This depicts a blacksmith striking an iron rod. If the rod is held aligned with the Earth's magnetic field (septentrio=north, auster=south), the rod becomes magnetised. Gilbert (1544-1603) was a physician, but performed extensive experimental work on magnetism. De Magnete is a classic of experimental science, and is often regarded as the first great work of science to be written in England.