Bullialdus, Ismael

, a celebrated astronomer and scholar, was born of protestant parents, at Houdun in France, September the 28th, 1605; and having finished his studies in philosophy at Paris, and in civil law at Poictiers, he applied to mathematics, theology, sacred and profane history, and civil law, with such assiduity, that he became eminent in each of these departments, and acquired the reputation of an universal genius. As he had travelled for his improvement into Italy, Germany, Poland, and the Levant, he formed an extensive acquaintance with men of letters, and maintained a correspondence with the most distinguished persons of his time. Although he had been educated a protestant, he changed his profession at the age of 27 years, and became a catholic priest. His life was prolonged to his 89th year; and having retired to the abbey of St. Victor at Paris in 1689, he died there November the 25th, 1694. Besides his pieces concerning ecclesiastical rights, which excited | attention, and the history of Ducas, printed at the Louvre, in 1649, in the original Greek, with a Latin version and notes, he was the author of several other works, chiefly mathematical and philosophical. His “Treatise on the Nature of Light” was published in 1638; and his work entitled, “Philolaus, sive de vero Systema Mundi,” or his true system of the world, according to Philolaus, an ancient philosopher and astronomer, in the same year, and republished in 1645, under the title of “Astronomia Philolaica,” grounded upon the hypothesis of the earth’s motion, and the elliptical orbit described by the planet’s motion about a cone. To which he added tables entitled “Tabulæ Philolaicæ:” a work which Riccioli says ought to be attentively read by all students of astronomy. He considered the hypothesis, or approximation of bishop Ward, and found it not to agree with the planet Mars; and shewed in his defence of the Philolaic astronomy against the bishop, that from four observations made by Tycho on the planet Mars, that planet in the first and third quarters of the mean anomaly, was more forward than it ought to be according to Ward’s hypothesis; but in the 2d and 4th quadrant of the same, the planet was not so far advanced as that hypothesis required. He therefore set about a correction of the bishop’s hypothesis, and made it to answer more exactly to the orbits of the planets, which were most eccentric, and introduced what is called by Street, in his “Caroline Tables,” the Variation: for these tables were calculated from this correction of Bullialdus, and exceeded all in exactness that went before. This correction is, in the judgment of Dr. Gregory, a very happy one, if it be not set above its due place; and be accounted no more than a correction of an approximation to the true system: For by this means we are enabled to gather the coequate anomaly a priori and directly from the mean, and the observations are well enough answered at the same time; which, in Mercator’s opinion, no one had effected before. It is remarkable that the ellipsis which he has chosen for a planet’s motion, is such a one as, if cut out of a cone, will have the axis of the cone passing through one of its foci, viz. that next the aphelion.

In 1657, was published his treatise “De Lineis Spiralibus, Exerc. Geom.& Astron.” Paris, 4to. In 1682 came out at Paris, in folio, his large work entitled, “Opus novum ad Arithmeticam Infinitorum:” a work which is a | diffuse amplification of Dr. Wallis’s Arithmetic of Infinites, and which Wallis treats of particularly in the 80th chapter of his historical treatise of Algebra. He wrote also two admonitions to astronomers. The first, concerning a new star in the neck of the Whale, appearing at some times, and disappearing at others. The 2d, concerning a nebulous star in the northern part of Andromeda’s girdle, not discovered by any of the ancients. This star also appeared and disappeared by turns. And as these phenomena appeared new and surprizing, he strongly recommended the observing them to all that might be curious in astronomy. ¹