It was Sir John Herschel who remarked that “previous to the publication of the ‘Novum Organum’ natural philosophy, in any legitimate and extensive sense of the word, could hardly be said to exist.” In the address presented in 1623 by the University of Oxford to Sir Francis Bacon, he is represented “as a mighty Hercules who had by his own hand greatly advanced those pillars in the learned world which by the rest of the world were supposed immovable.” Treating of the electric fluid, Bacon has given (“Physiological Remains,” London, 1648) a detailed list of attractive and non-attractive bodies and the results of his very extensive experiments and observations in physical science generally, as well as of the investigations contained in Dr. Gilbert’s work. To the latter, however, many allusions had already been made in Bacon’s “The Advancement of Learning,” published during 1605, two years before he was made Solicitor-General. The most satisfactory analyzation of Bacon’s researches is to be found in the attractive edition of his complete works published by Spedding, Ellis and Heath, fifteen volumes, Boston, 1863. Therein will be seen the following references to the magnet and magnetic virtue: Vol. I. p. 435 (note). In Gilbert’s philosophy, the earth’s magnetic action is not distinguished from gravity (De Mundo, II. c. 3). That the magnetic action of the earth or of a magnet is confined to a definite orb, appears from a variety of passages (see “De Magnete,” II. c. 7, and the definitions prefixed to this work). Gilbert distinguished between the “Orb of Virtue” which includes the whole space through which any magnetic action extends, and the “Orb of Coition” which is _totum illud spatium per quod minimum magneticum per magnetem movetur_. He asserts that the orb of the magnetic virtue extends to the moon and ascribes the moon’s inequalities to the effects it produces (“De Mundo,” II. c. 19).