Public Domain Mark
You can use this work for any purpose without restriction under copyright law. Read more about this licence.
Credit
A treatise of artificial magnets ; in which is shewn an easy and expeditious method of making them, superior to the best natural ones, and also, a way of improving the natural ones, and of changing or converting their poles : Directions are likewise given for making the mariner's needles. In the best form, and for touching them most advantageously, &c / by J. Michell. Public Domain Mark. Source: Wellcome Collection.