This treatise, in which the proposition that the Earth is a giant magnet is put forth, was the first major scientific work produced in England. Its author, William Gilbert, was a Fellow of St John's and an eminent physician. Alongside his medical profession Gilbert conducted experiments on magnetism, of which this volume was the fruit. In it Gilbert explored all previously accepted knowledge regarding magnetism using an inductive, experimental method that preempted the one described by Francis Bacon later in the 17th century. He examined the attractive power of magnets, their use in navigation, the orientation of magnets towards the poles, and also included the first ever treatise on electrical phenomena, introducing the word "electric" into the language. The work was of such key importance that it later influenced scientists such as Kepler, Newton, and particularly Gallileo. In spite of the apparent modernity of his work, Gilbert held on to an animistic notion of the physical world, perceiving magnetism as the "soul" of the planet.

Details of a book owned by Gilbert in St John's Library.