Cabæus was the first to observe electrical repulsion, and he thus announces his discovery in the tenth chapter of the above-named work: “Magnetic attractions and repulsions are physical actions which take place through the instrumentality of a certain quality of the intermediate space, said quality extending from the influencing to the influenced body.... Bodies are not moved by sympathy or antipathy, unless it be by means of certain forces which are uniformly diffused. When these forces reach a body that is suitable they produce changes in it, but they do not sensibly affect the intermediate space nor the non-kindred bodies close by it....”
The “Philosophia Magnetica” is the second Latin book published on electricity, Gilbert’s “De Magnete” being the first.
References.—Becquerel, “Résumé,” Chap. III; Stuello, “Bibl. Scrip. S. J.,” Rome, 1676; Francisco de Lanis, “Magist. nat. et artis,” 1684; L. L. de Vallemont, “Description de l’aimant,” 1692, pp. 167, 170; Dechales C. F. Milliet, “Cursus seu Mundus Mathem.,” 1674, 1690.
A.D. 1632.—Sarpi (Pietro)—Fra Paolo Sarpi—Father Paul—Paulus Venetus—Paolo Sarpi Veneto (b. 1552, d. 1623), who was the author of the celebrated history of the Council of Trent (“the rarest piece of history the world ever saw”) is referred to by Gilbert in “De Magnete,” Book I. chap. i. Therein, he says that Baptista Porta, who has made the seventh book of his “Magia Naturalis” a very storehouse and repertory of magnetic wonders, knows little about the movements of the loadstone and never has seen much of them, and that a great deal of what he has learned about its obvious properties, either through Messer Paolo, the Venetian, or through his own studies, is not very accurately noted and observed.
In the introduction to the 1658 edition of his “Natural Magick,” Porta admits that he gained some knowledge of Sarpi, who, says he, is of all men he ever knew the most learned and skilful and the ornament and splendour not only of Venice or of Italy, but of the entire world. Bertelli refers (“Memor. sopra P. Peregrino,” p. 24, note) to P. Garbio’s “Annali di Serviti,” Lucca, 1721, Vol. II. pp. 263, 272, 274, and to Fra Fulgenzio Micanzio’s “Life of Sarpi,” Helmstat—Verona, 1750, in which it is stated that not only Porta but likewise a celebrated ultramontane studied magnetism under him. Garbio asks: “Could this ultramontane be Gilbert of Colchester?”
By Griselini (“Vita de Fra P. Sarpi”—memoria anecdote—Lausanne, 1760), Paolo is said to have written a treatise on the magnet and to have therein recorded many observations, including the earliest mention that magnetic properties are destroyed by fire.
Bertelli—whose afore-named memoir we must confine ourselves to, as it is more satisfactory than are the accounts elsewhere given—makes mention that he has had in his possession, by courtesy of Sig. Giuseppe Valentinelli, the Royal Librarian of the Marciana at Venice, copy of a manuscript (Cod. CXXIX, classe 2, MS. Ital.) containing a brief comparison of Sarpi’s magnetic researches with those of Musschenbroek. This manuscript is again alluded to by Bertelli (Memor., p. 88) wherein it is said that lines 5–38 of the first column, p. 170, are headed “Observations of F.P.S. on the loadstone, collated with P. Musschenbroek’s Researches,” and embrace five paragraphs translated as follows:
1. The author had first tried the action of one magnet on another without entering into the question of calculation, but modern authors have, in view of the observations made, endeavoured to discover a method of computing magnetic forces in any proportion to the distances, and in the same better regulated systems they have discovered the cause to be uncertain (or varying) owing to the contemporaneous action of magnetic repulsion.
2. He was acquainted with the well-known action of the magnet on iron, but he understood—as even at this day some understand—that it was caused by the atmosphere. New experiments have made us seriously doubt this. He did not pay attention to the proportion of the magnetic forces as compared with the distances of iron, to the discovery of which the efforts of present philosophers are directed but in vain. He saw, however, that the facility or difficulty of attraction depends upon the size of the iron (maximum and minimum).
3. He was not ignorant of the direction of the magnet and of iron rubbed with the magnet towards certain quarters of the sky when he mentions the new discovery of the poles in the magnet, and the variation of the magnetized needle, from the Northern or the Southern quarters, but he did not know a greater number than two poles found in the magnet, the variation of the declination, or, I should rather say, the uncertainty of the variation and the different inclinations of the needle at different places on the earth.