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ERA those ecclesiastical principles which have become connected with his name under the long-familiar designation of Erastianism. But there was found among his papers after his death an essay entitled "Explicatio gravissimæ quæstionis, utrum excommunicatio mandato nitatur divino, an excogitata sit ab hominibus," which was published by Castelvetro who had married his widow. This tract was confuted by Beza in his tracts De Presbyteris and De Excommunicatione, and thus became known to the divines of Britain. The English Erastians formed a considerable party in the ecclesiastical contests and troubles of the seventeenth century, and the name of the Heidelberg physician and professor is still, as we all know, applied to the views of those who deny and oppose the autonomy of the church, and would subject her discipline and government to the control of the state.—P. L.  ERATOSTHENES, successor of Aristarchus in the school of Alexandria, was born at Cyrene, 276. He has claims to be regarded as the father of astronomy and geography. Considerable advances had been made previous to his time; but to him is due the credit of elevating them to the rank of exact science. He was called by Ptolemy Euergetes to take charge of the Alexandrian library, and he continued in his office till the reign of Ptolemy Epiphanes. The former monarch, having discovered his love for astronomical science, engaged him to construct improved instruments for the observatory. The armillary sphere was now executed with a degree of accuracy which had not hitherto been attained. Eratosthenes, indeed, has been usually cited as the inventor of this instrument. This, however, is not correct, as it was well known, long previous to his time, both to the Chinese and the Arabs. He had, however, the merit of perfecting the instrument, and obtaining from it far more accurate results than any previous astronomer could boast of. There is some doubt as to the precision with which observations could be made by the sphere. Proclus gives us the size of the circle used at the Alexandrian observatory; but he uses a measure the exact value of which cannot be determined at the present day. Flamsteed, however, on a full investigation of the subject, arrived at the conclusion that the circle could not be less than three feet in diameter. On the line of such a circle a graduation down to 5´ would be distinguishable. It is of much importance, in reference to the astronomy of the present day, that some notion should be formed of the degree of exactness attained by the Alexandrian instruments; for some of the nicer problems depend on the change of astronomical elements that has since taken place. It may be a question whether the difference between his observations and those of more modern times is due merely to the error of instruments, or to a real change in the astronomical elements. It is the most probable conclusion that the Alexandrian instruments attained a very reliable degree of accuracy, though of course not to be compared to the instruments of modern time, which by the aid of the telescope have attained an incalculably greater precision. It might be thought that by enlarging the graduated circle, the Alexandrian observers might have attained much greater accuracy, as the limb of the instrument might have a graduation much more minute. Ptolemy, however, understood the fallacy of this, and guarded against too cumbrous circles. He knew that minute graduations would only give a fallacious accuracy, while the powers of vision were limited to larger spaces in the heavens. The name of Eratosthenes will ever be associated with the precise determination of the obliquity of the ecliptic—one of the most important astronomical elements. By astronomers before his time the obliquity was roughly estimated at 24°. Eratosthenes, however, saw the importance of a precise determination, and, by measuring the distance between the summer and the winter solstice, he arrived at the result that the precise obliquity was 23° 51´ 15´´. Though he understood the importance of the determination, he could not foresee its bearing on gravitation, and the striking confirmation it was to give to the most recondite results of theory. It was found that modern determinations of the obliquity did not at all coincide with the observations of Eratosthenes, and that the difference was so great that instrumental errors could not well explain them. Intermediate observations suggested the explanation that the obliquity might be diminishing, and for a long time the subject was keenly contested amongst astronomers. The theory of gravitation at last gave a full solution of the difficulty. It was shown to be a necessary result of theory, that the obliquity should slowly diminish to a certain extent, and then increase. It was at first thought that the ecliptic would at last coincide with the equator, so that we would have perpetual spring. It was, however, shown that the ecliptic oscillated between narrow limits. Eratosthenes gained still greater fame by his determination of the magnitude of the earth. In the case of the ecliptic his credit was merely that of the observer; in the case of the earth's measure he displayed the originality of genius. It was a problem the method of solving which was altogether unknown, and he has not only the credit of devising the method, but of carrying out the determination with consummate skill. His method is precisely the method adopted at the present day. He measured a degree on the earth's surface, and having found the length of one degree, the length of three hundred and sixty degrees, or the earth's circumference, was at once determined. Considering the great difficulty of the operation, it is matter of surprise that his approximation is so close. Having thus discovered the circumference, and therefore the diameter of the earth, he was the first to apply a measuring wand to the solar system to ascertain its actual dimensions. Formerly only proportions were known in reference to the distances of the bodies of the solar system; now absolute dimensions were determined. Eratosthenes was also great as a geographer. He constructed maps, with parallels to mark the position of places. He anticipated modern geologists by liberally employing physical convulsions to explain the appearances on the earth's surface. His genius was almost universal. He was not only great in the physical sciences, but he enjoyed high distinction as a poet and philosopher. Only fragments of his works have come down to us. He died about the year 196 .—W. L. M.  ERBA,, a violinist, lived at Rome in 1730, and is supposed to have been born in Milan. He published "Sonate da Camera a violino solo e basso" at Amsterdam in 1736, which is the only trace that remains of his talent. The name of this insignificant musician has lately been dragged into notice by the attempt of some critics to father upon him the Magnificat, from which several pieces are appropriated in the oratorio of Israel in Egypt—an attempt founded on the accident of a copy of the work (once the only one known) in the possession of the Sacred Harmonic Society, being superscribed "dal Signor Erba;" an accident probably arising from the MS. having once belonged to some person so named. This supposition is disproved, however, by the discovery of the original copy of the Magnificat in Handel's writing, and the author of the violin sonatas may now return to his long obscurity.—G. A. M.  ERCHINOALD, Mayor of Neustria, flourished in the first half of the seventh century. He was a relative of Haldetrude, the first wife of Clotaire II. and mother of Dagobert I. He was elected mayor of the palace in Neustria in 640 to Clovis II., whom he married in 649 to Bathilda, a Saxon slave purchased by him from some English pirates. On the death of Clovis in 656, Erchinoald, in conjunction with Bathilda, assumed the guardianship of Clotaire, Childeric, and Thierry, the sons of the deceased monarch. He died in 660, after having held the reins of government for twenty years.—J. T.  ERCILLA Y ZUNEGA,, born at Bermeo, 1533, the son of a learned jurisconsult, was made page to the Infanta Philip, son of Charles V., and accompanied his royal master on a tour through the greater part of Europe. In 1554, being then only twenty-one years old, he came to England in the suite of Philip, on the occasion of his marriage with Queen Mary. While in this country, intelligence reached him of the rebellion which had broken out in the diminutive province of Arauco, on the coast of Chili; and he was one of the adventurers who followed in the train of Garcia de Mendoza, son of the viceroy of Peru. Ercilla fought in seven battles, and on one occasion escaped death still more narrowly, having been condemned, and actually brought on the scaffold, for some breach of discipline arising out of a tournament. The chief feature of interest, however, for us is the poem entitled "La Araucana," which he composed during his wanderings—the only poem of that eventful time which has gained for its author an enduring reputation. Written in the intervals of an adventurous life, often on such scraps of leather as might be at hand, this poem is a true epic; and if it does not deserve the indiscriminate praise of Voltaire, has yet many of the highest qualities that mark literary excellence. It is historically and geographically accurate, and gives a vivid picture of the life of those early conquerors. The speeches put into the mouths of 