Note 32 — Book I

Sir Kenelm Digby (“Treatise of the Nature of Bodies,” 1645, Chap. XX. p. 225) says that the manner in which Gilbert “arrived to discover so much of magnetical philosophy” and “all the knowledge he got on the subject, was by forming a little loadstone into the shape of the earth. By which means he composed a wonderful designe, which was to make the whole globe of the earth maniable; for he found the properties of the whole earth in that little body ... which he could manage and try experiments upon at his will....” In the note at p. 47 (P. Peregrinus, A.D. 1269), it will be seen that the terrella was constructed by both in practically the same manner: only Peregrinus considered it “a likeness to the heavens,” whilst Gilbert regarded it as the earth itself.