CHAPTER IX.

AMONG the men of the past, whose true greatness the world is only now tardily appreciating, stands Pietro Sarpi,' better known by his monastic name of Fra Paolo, for he was a friar of the Servite order. He was born in 1552, and died in 1623. The erection of his statue-the highest honor which the Republic of Venice could bestow upon a citizen-was decreed three weeks after his death, and carried into effect two hundred and seventy years later.

It is not my province to recount the strange history of Fra Paolo's political career; wherein, by sheer force of ability, he successfully opposed the Pope in the plenitude of his power, and became the chief consulter, guide and de facto ruler of the proudest state in Europe. The greatest of the Venetians was equally, in his day, the greatest of Italian scientists. A history of any branch of physical science, known in his time, must of necessity deal with some part of his work.

"What he did," says Macaulay, "he did better than anybody;" and, perhaps, it will suffice to recall Galileo's reverent address to him, as "my father and my master," to show that the encomium of the historian applies not alone to his achievements as a statesman. His private secretary and intimate friend, Fra Fulgenzio Micanzio, in a list of subjects in which he declares Fra Paolo to have been profoundly versed, mentions, besides the Hebrew and Greek languages, and mathematics, "history, astronomy, the nutrition of life in animals, geometry, including conic sections, magnetism, botany, mineralogy,

1Robertson: Fra Paolo Sarpi, London, 1894. Griseleni: Vita de F. P. Sarpi, 1760. Giovini: Vita, etc., Brussels, 1836. Micanzio: Vita, etc., Verona, 1750. Fabronio: Vitæ Italorum, Pisa, 1798, xvii.

hydraulics, acoustics, animal statics, atmospheric pressure, the rising and falling of objects in air and water, the reflection of light from curved surfaces, spheres, mechanics, civil and military architecture, medicine, herbs" and "anatomy." And, in almost every one of these great fields, Sarpi made discoveries of the highest importance. He first observed the dilatation and contraction of the uvea of the eye; first found the valves in the human veins, and first discovered the circulation of the blood (Harvey experimentally demonstrated this afterwards), and invented artificial respiration. He made the first maps of the moon, anticipated Kepler in his observations on the reflection of light from curved surfaces, first recognized the effects of refraction, and declared that the sun is fed, and that stars are suns. He announced that heat is motion, and exemplified its generation by heating iron with a hammer; that light is motion, and that it comes to us in waves or pulsations through a medium less material than the atmosphere; that sound is motion, but not (as he thought) motion of the atmosphere, for it travels against the wind and through water, moving like light in waves or pulsations; that color is caused by the atmosphere and by the reflection of different rays of light; and then he identifies sound, color, heat and light together, thus correlating these physical phenomena. The desire is strong to dwell upon Sarpi's researches in these fields, but it must be foregone to turn to his discoveries in magnetism. Unfortunately, here the actual records are meagre. He wrote a treatise on the magnet, which, after his death, remained, with his other manuscripts, in the Servite Monastery, where he spent his life. As late as 1740 his literary remains were minutely examined and arranged in order by the learned Fra Giuseppe Bergantini. Twentysix years afterwards they, with the buildings in which they were stored, were completely destroyed by fire.

While Sarpi's original treatise on the magnet was thus lost, a brief record of its contents is contained in his biog

raphy, written by Griselini, and published about 1760. It appears to have contained, first, a mass of scattered data (probably lecture notes), followed by 140 propositions, based on magnetic phenomena. They relate to the discovery of the two points or poles of greatest attraction on the magnet by means of the inclined magnetized needle and to the "new generation of the same;" to magnetic attraction and repulsion, and the communication of magnetism, both from the lodestone and from magnetized iron; to the increase of magnetism in magnetic bodies; to the action of one magnet upon another; to the various effects produced "in the sphere of the horologe through different positions of magnetized bodies with respect to it;"" to the irreparable loss of magnetism which happens in the lodestone and in magnetized bodies when submitted to fire; and, finally, to the magnetization of iron, by means other than by rubbing it with a lodestone.

Another volume of Sarpi's writings, the original of which was also destroyed in the same fire, contained 674 propositions or "Pensieri" on all kinds of subjects, pertaining to every branch of natural science. Fortunately, a copy2 was made of this before its destruction, which is now in the Library of St. Mark in Venice. Accompanying the manuscript are notes, made during the last century, in which Sarpi's discoveries are compared with those then claimed by Peter Van Musschenbroeck of Leyden. This gives a little clearer idea of Sarpi's investigations, in that it states that he determined the reciprocal relation of one magnet upon another, but did not measure or determine the magnetic force: also the action of the magnet on iron: also the manifestation of magnetic activity around the poles as an atmosphere-or in other words the field of force: also the maximum and minimum of attractive force of the magnet on the iron according to the magnitude of

'This may possibly relate to the supposed rotary sphere of Peregrinus. 2 Class II., No. cxxix., cited by Bertelli, Mem. Sopra Peregrinus, p. 88.

CESARE'S DISCOVERY.

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the mass of the latter: also the inversion of polarity which may take place during the magnetization of the needle, although he seems to have known nothing of consequent poles: also magnetic variation (but not the variation of the variation) and magnetic inclination: also the magnetic properties acquired by iron "freely exposed to the air."

Robert Norman's book, to which I have referred in the preceding chapter, was published a few years before Sarpi is believed to have made his principal magnetical investigations; and it is altogether unlikely that it escaped the friar's attention. The Letter of Peregrinus had been in print for more than two decades. Moreover, a manuscript of it existed, and was at Sarpi's disposal in the Castellan Library of Venice. We are therefore justified in eliminating from the two categories, before given, all matters anticipated by Norman and Peregrinus, so far as these can be recognized. This done, the net result is to leave the destruction of magnetism by fire, the magnetization of iron by means other than induction from a lodestoneafterwards alluded to as the acquirement of magnetic properties by iron freely exposed to air-and the existence of the field of force around the magnetic poles, now directly made known for the first time.

That a lodestone could be deprived of its attractive quality by heating it to a high temperature was a new discovery, which may well have excited the incredulity of those who believed with Norman that the virtue in the stone was implanted by Providence, and hence was presumably ineradicable. The revelation that iron could be magnetized without the aid of the stone at all was not original with Sarpi, but was the result of an accidental observation made by one Giulio Cesare, a surgeon of Rimini, early in 1586, and not long before Sarpi wrote concerning it. An iron rod which supported a terra-cotta ornament upon the tower of a church in the before-named town had become bent by the force of the wind, and had remained thus distorted for about ten years. It was taken

down and the iron sent to a blacksmith to be straightened, and while it lay in the smithy, Cesare, by chance, noticed that it possessed attractive properties. By an odd coincidence the church was dedicated to St. Augustine; so that one might almost fancy that the influence of the Saint whose discoveries concerning the magnet have already been noted, was somehow still potent to lead others in the same path. The circumstance puzzled the philosophers greatly; for how, they asked, could iron which is a metal be thus converted into lodestone which is a stone? For the time being the old doctrine of sympathies and similitudes the great likeness and sympathy between iron and magnet-furnished a sufficient answer: but after a few years the true explanation appeared in a great work, to which the orderly progress of this narrative forbids further reference at present.1

Although the limiting of Sarpi's magnetic discoveries to the destruction of magnetism by heat, and the apparent concentration at the poles of the atmosphere or virtue which Norman thought to be spherical seems to be the consequence of the process of exclusion followed, it would be unjust to the great Consultore to assume that there are here defined the actual metes and bounds of his accomplishments in magnetic research. The evidence so far adduced concerning them is at best imperfect; while it must be remembered that to depreciate their importance or to obliterate them wholly, powerful forces have acted for centuries.

Still, to have conceived the first clear idea of the field of force about the poles of a magnet is sufficient to give the discoverer an undoubted pre-eminence, and that Sarpi did this is not only indicated by a comparison of his reputed achievements with what was already known, but is strongly substantiated by the efforts which have been made to deprive him of all credit for them. Sarpi had no worse enemies than the Jesuits, whom he caused to be

'Aldrovandus: Musaeum Metallicum. Milan, 1648, lib. 1, 134.