ceit. It was disproved in 1609 by A. Boetius de Boot; celebrated in Latin verse by Famianus Strada in 1617-metrical translations by Hakewill in his Apologie 1630, and by Ward in The Wonders of the Loadstone, 1640; denounced in 1629 by Cabeo, who gives the first drawing of the telegraph on p. 302; railed at by Galileo in 1632; described in fine prose by Addison in Spectator 241 (1711), and in elegant verse by Akenside in Book III of his Pleasures of the Imagination, 1744.

References, descriptions, illustrations, approval or condemnation of the sympathetic compasses will be found in forty works in the Library, including the detailed account given by Daniel Schwenter (J. H. De Sunde) in his Steganologia, 1600, and an interesting form of the story by Glanvill in his Scepsis Scientifica; or Confest Ignorance the way to Science, 1665.

Anti-Copernican writers are strongly represented by Kircher, Cabeo, Schott, Riccioli, Leotaud, Grandami, Dechales and Scarella. The ponderous tomes on physical and cosmical science written by these men make one wonder that the system of the world put forward in 1543 by the Canon of Frauenburg, and based by him on rather slender arguments, had vitality enough to survive the blows dealt by such a galaxy of churchmen, mathematicians, and astronomers.

Gilbert, on the other hand, was a staunch advocate of the Copernican theory, which he sought to confirm by "new and unheard-of" arguments derived from his study of the laws and phenomena of magnetism which he carried on for twenty years in his workshop at Colchester. Having shown

by original experiments and some artful argumentation that the earth acts as a colossal magnet, he proceeded to infer that its revolution is due to a "magnetic compact" or "alliance" between the sun and the earth, for "the sun itself is the mover and inciter of the universe." This magnetic theory of the movements of the various members of the solar system was, nevertheless, a very weak point in Gilbert's armor which his continental opponents were not slow in detecting, and which, together with his errors on dip and variation, they assailed with all the bolts of their well-filled quivers. The cause of Copernicanism was not served, and Gilbert's work fell into disrepute. The curious episodes of this anti-Gilbertian warfare make very interesting reading in the works enumerated above.

Verbal curiosities hastily gleaned from works in the Library would include the coinage of the term affinity by Albertus Magnus, barometer by Boyle, gas by van Helmont, magnetic inclination by Bond, electric circuit by Watson, electric potential by Green, galvanometer by Cumming, electromagnet by Sturgeon, and telephone by Wheatstone. The term electricity occurs for the first time in Sir Thomas Browne's Pseudodoxia Epidemica, 1646, page 51 and the plural noun electricities on page 79; magnetism occurs in Barlowe's "Magneticall Advertisements," 1616; while 'Hɛnt pouay vntióμós, electro-magnetismos, is the astonishing title which Father Kircher gives to a chapter of his Magnes, sive de Arte Magnetica, 1641, beginning on page 640.

9 Laplace introduced the concept of the potential function into analytical investigations, but limited its use to problems in gravitation. Green gave the function its name and extended its application to electricity and magnetism.

The magnetic needle, when used by European navigators, was floated by means of straws, wood, or cork. Sometimes, too, it was laid across the edge of a light bowl which floated in water contained in a larger vessel. Abbot Neckam at the end of the twelfth century, wrote of a needle suspended on a dart (jaculum); Peregrinus introduced the double-pivoted needle in 1269; a filar mode of suspension was devised by Camillus Leonardus and described by him in his Speculum Lapidum, 1502. The copy of this work, which is in the Library, is dated 1610; the translation, 1750. Stirrups for suspending magnets appear on page 28 of Canon Tarde's Usages du Quadrant à l'esguille aymantée, 1638.

Two remarks of Bishop Wilkins may here be noticed. The first occurs in his Mathematicall Magick, 1648, and states that the "mariner's needle" may be used to steer a boat running under water-a fact which is well known to those who man our submarines. The second remark occurs in his Mercury; or the secret and swift messenger, 1641, and refers to a machine of which it is said: "When the friend to whom it is sent shall receive and open it, the words shall come out distinctly and in the same order as when they were spoken." This is a near approach to the mechanical reproduction of sound by our modern phonographs.

Another illustration of the aphorism nil sub sole novi, will be found in a passage of the Philosophe sans Prétentions, ou l'homme rare, published in Paris in 1775, in which the impact of light or the pressure due to radiation is used for the purpose of doing mechanical work. The words of "D. L. F.," the author, are: "Observez que la percussion de la lumière

agit actuellement au-dessous de ma méchanique, c'est elle qui va m'enlever sans beaucoup d'efforts," p. 32. The work was, of course, one of pure imagination.

Of the beginnings of electricity, copious references will be found to amber and jet and their attraction for straws, chaff, and light bodies. The first original work of any extent on the general subject is Book II, of Gilbert's De Magnete, 1600, which, though abounding in original experiments on electrical attraction, makes no mention whatever of electrical repulsion. It stands out as a singular fact in the history of electrical discovery that an experimenter of Gilbert's diligence and ability should have failed to detect the mutual action of similarly electrified bodies, the discovery of that capital effect being reserved for Cabeo, who carefully describes it on page 194 of his Philosophia Magnetica, 1629, the description being here reproduced.

Apropos of nomenclature, Robert Symmer recognized in his New Experiments and Observations, 1760, that “negative electricity is in reality a positive, active power," a remark which appears to be justified by the activity and energy of our contemporary electrons, or atoms of electricity, as well as by a number of other electrical phenomena.

The evolution of the Leyden jar may be studied in the works of Winkler, of Leipzig, and Musschenbroek, of Leyden, and notably in the letters which Franklin wrote to his friend Collinson, of London, 1747-49. It is sometimes stated that Franklin was the first to ignite gunpowder by means of the electric spark, and that he did so in June, 1751. This is an error, inasmuch as Dr. Watson describes, in his

Experiments and Observations, 1746, page 40, a method which he successfully employed for firing gunpowder. Watson's book was well known to Franklin.

The development of the electrical machine may be followed from the sulphur-ball of von Guericke to the glassglobe of Newton, the glass-cylinder of Andrew Gordon, the Benedictine, the plate-machine of Martin de Planta of Sus in Switzerland, 1755, and the double-cushion plate-machine of Sigaud de la Fond, 1756. It will be seen that Winkler, of Leipzig, substituted for the palm of the hand-which was the rubber of early times—a leather cushion, which Canton afterwards covered with an amalgam of tin and mercury, thereby greatly increasing the output of the machine.

Among Galvani's predecessors the first place belongs to the celebrated Dutch naturalist, Swammerdam, who describes in his Biblia Natura, page 839, experiments which he made in 1658 in presence of his munificent patron the Grand Duke of Tuscany, and in which he obtained muscular contractions of frogs' legs by using a pair of silver and copper wires.

Analogous experiments were made in 1784, and published in 1786 by Cotugno, professor of anatomy in the University of Naples, to the effect that he felt a benumbing sensation in his hand while dissecting a mouse which had bitten one of his students; but it was not, however, until Galvani published in his De Viribus Electricitatis, 1791, an account of experiments which he began in 1786, that the subject of "animal electricity," as it was called, commenced to attract serious attention.

Among Volta's predecessors should be reckoned Sulzer,