“In the discovery of secrets and in the investigation of the hidden causes of things, clear proofs are afforded by trustworthy experiments rather than by probable guesses and opinions of ordinary professors and philosophers. In order, therefore, that the noble substance of that great magnet, the earth, hitherto quite unknown, and the exalted powers of this globe of ours may be better understood, I shall first of all deal with common magnets, stones, and iron materials, and with magnetic bodies, and with the near parts of the earth, which we can reach with our hands and perceive with our senses. After that I shall proceed to show my new magnetic experiments, and so I shall penetrate for the first time into the innermost parts of the earth. “After I had seen and thoroughly examined many of those things which have been obtained from mountain heights and ocean depths, or from deep caves and hidden mines, I applied much prolonged labour on investigating magnetic forces, which surpass in wonder all other things about us. This labour has not been idle or unfruitful, since daily, during my experimenting, new and unexpected properties came to light. In this manner my knowledge has increased so much through actual observation, that I felt able to explore the interior parts of our globe, and explain its substance upon magnetic principles, and to reveal to mankind the earth, our common mother, and point it out, as if with the finger, by real demonstration and by experiments appealing to the senses. “As geometry ascends from very small and very easy principles to the greatest and most difficult, so our magnetic doctrine and science sets forth in convenient order the things which are less obscure. From these have come to light others that are more remarkable, and at length in due order are opened the concealed and most secret things of the globe of the earth, and the causes are made known of those things which either through the ignorance of the ancients, or the neglect of moderns, have remained unrecognised and overlooked.” Dr. Gilbert then proceeds to ask why he should expose himself to the violent attacks and criticisms of men, calling themselves learned though unacquainted with the facts:--