X. MAGNETISM.
For proper understanding of the Thirteenth Century scholars, it is especially important to appreciate their thoroughly scientific temper of mind, their powers of observation, and their successful attainments in science. I know no more compendious way of reaching the knowledge of these qualities in the medieval mind, than a study of the letter of Peregrinus, which we would in our time call a monograph on magnetism. Brother Potamian, in his chapter in "Makers of Electricity" (Fordham University Press, N. Y., 1909) on Peregrinus and Columbus, sums up the very interesting contributions of this medieval student of magnetism to the subject. The list of chapters alone in Peregrinus' monograph (Epistola) makes it very clear how deep were his interests and how thoroughly practical his investigations.
THE DOUBLE PIVOTED NEEDLE OF PEREGRINUS.
They are:—"Part I., Chapter i, purpose of this work; 2, qualifications of the experimenter; 3, characteristics of a good lodestone; 4, how to distinguish the poles of a lodestone; 5, how to tell which pole is north and which is south; 6, how one lodestone attracts another; 7, how iron touched by a lodestone turns toward the poles of the world; 8, how a lodestone attracts iron; 9, why the north pole of one lodestone attracts the south pole of another, and vice versa; 10, an inquiry into the natural virtue of the lodestone.
"Part II., Chapter 1, construction of an instrument for measuring the azimuth of the sun, the moon or any star then in the horizon; 2, construction of a better instrument for the same purpose; 3, the art of making a wheel of perpetual motion."
In order to illustrate what Peregrinus accomplished it has seemed worth while to reproduce here the sketches which illustrate his epistle. We have the double pivoted needle and the first pivoted compass.
In the light of certain recent events a passage from the "New Naval History or Complete Review of the British Marine" (London, 1757) is of special interest. It illustrates perhaps the new confidence that came to men in sailing to long distances as the result of the [{443}] realization of the practical value of the magnetic needle during the Thirteenth Century.
FIRST PIVOTED COMPASS (PEREGRINUS, 1269).
"In the year 1360 it is recorded that a friar of Oxford called Nicholas de Linna (of Lynn), being a good astronomer, went in company with others to the most northern island, and thence traveled alone, and that he went to the North Pole, by means of his skill in magic, or the black art; but this magic or black art may probably have been nothing more than a knowledge of the magnetic needle or compass, found out about sixty years before, though not in common use until many years after."