JOHN FRANCIS, a French mathematician, was born at Paris in the year 1613. Having finished his academical studies, he entered into the order of the Minims, and took the habit in 1632; and, as is usual, he changed the name given him at his baptism for that of Francis, the name of his paternal uncle, who was also a Minim, or Franciscan. His inclination and taste for the mathematics ap- peared early during the course of his philosophical studies; and to that science he devoted what time he could spare from his other employments, after he had completed his studies in theology. All the branches of the mathematics, however, did not equally engage his attention; he confined himself particularly to optics, and only learned as much of the rest as was necessary for rendering him perfect in this branch. He has himself informed us, in the preface to his *Thaumaturgus Opticus*, that he travelled twice to Rome, and that, on his return home, he was appointed teacher of theology. He was afterwards chosen to accompany Father Francis de la Noue, vicar-general of the order, in his visitation of the convents throughout France. The eagerness of his passion for study, however, induced him to make the best use of all the moments he had to spare, and that wise economy of time furnished him with as much leisure as satisfied his love of knowledge. Being taken sick at Aix, in Provence, he died there on the 22d of September 1646, at the early age of thirty-three. He was an intimate acquaintance of Descartes, who had a high esteem for him. The principal works of Niceron are, 1. *L'Interpretation des Chiffres, ou Règles pour bien entendre et expliquer facilement toutes sortes des Chiffres simples*, Paris, 1641, in 8vo; 2. *La Perspective Curieuse, ou Magie Artificielle des effets merveilleux de l'Optique, Catoptrique, et Dioptrique*; 3. *Thaumaturgus Opticus, sive admiranda Optices, Catoptrices, et Dioptrices, pars prima*, 1646, in folio, a work to which the preceding essay was intended to serve as an introduction.

Niceron, John Peter, justly celebrated on account of his Biographical Memoirs, was born at Paris on the 11th of March 1685. He was descended of an ancient and noble family, which was in very high repute about 1540. He studied with success in the Mazarin College at Paris, and afterwards at the college of Duplessis. Having resolved to forsake the world, he consulted one of his uncles, who belonged to the order of Barnabite Jesuits. This uncle examined him, and not doubting his election, introduced him as a probationer to that society at Paris. He was received in 1702, took the habit in 1703, and made his vows in 1704, at the age of nineteen. After he had professed himself, he was sent to Montargis, in order to study philosophy and theology; and his superiors, being satisfied with his proficiency, sent him to Loches, in Touraine, to teach the classics and rhetoric. Here his devout behaviour and excellent conduct as a teacher made him be thought worthy of the priesthood, which he received at Poitiers in 1708; and as he had not arrived at the age to assume this order, a dispensation was obtained in his favour. The college of Montargis having recalled him, he there professed rhetoric for two years, and philosophy during four. Notwithstanding all these avocations, he was humanely attentive to every call of charity, and to the instruction of his fellow-creatures, many of whom heard his excellent discourses, not only in the pulpits of the churches within the province, but even in those of Paris. In 1716, his superiors invited him to the city, that he might have an opportunity of prosecuting with more convenience those studies for which he had always expressed the greatest inclination. He understood not only the ancient, but also the modern languages; a circumstance of infinite advantage in the composition of those works which he has given to the public, and which he carried on with great assiduity till the time of his death, which happened on the 8th of July 1738, at the age of fifty-three. His works are, 1. *Le Grand Fibrifuge, or, a Dissertation to prove that common water is the best remedy in fevers, and even in the plague* (translated from the English of John Hancock, minister of St Margaret's, London), in 12mo. This little treatise made its appearance, amongst other pieces relating to this subject, in 1770, and was attended with such success that it passed through three editions, the last of which appeared in 1730, in two vols. 12mo. 2. *The Voyages of John Ovington to Surat, and divers parts of Asia and Africa*, containing the history of the revolution in the kingdom of Golconda, and some observations upon silk worms, Paris, 1725, in two vols. 12mo. 3. *The Conversion of England to Christianity, compared with its pretended Reformation*, a work translated from the English, Paris, 1729, in 8vo. 4. *The Natural History of the Earth*, translated from the English of Mr Woodward, by M. Nogues, doctor in physic, with an answer to the objections of Dr Camerarius, and containing also several letters written on the same subject, with a methodical distribution of fossils, translated from the English by Niceron, Paris, 1735, in 4to. 5. *Memoirs of Men illustrious in the Republic of Letters*, with a critical account of their works, Paris, in 12mo. The first volume of this great work appeared in 1727; and the others were given to the public in succession, as far as the thirty-ninth, which appeared in 1738. The fortieth volume was published after the death of the author, in 1739. Since that period three others have been added; but in these there are many articles of which Niceron was not the author. To a work of this kind many objections may be made, according to the particular taste or views of each individual objector; and, in fact, the French critics have expatiated with much severity upon the mistakes unavoidable in an undertaking of such magnitude and difficulty. But it is much more easy to censure than to execute. Since the time of Niceron the French have produced no such collection as his, which, with all its faults, has been the foundation, as far as it goes, of all the subsequent accounts given of the same authors.

Nicetas, David, a Greek historian, a native, as some relate, of Paphlagonia, who lived about the end of the ninth century. He wrote the Life of St Ignatius, patriarch of Constantinople, which was translated into Latin by Frederic Mutius, bishop of Termoli; and he also composed several panegyrics in honour of the apostles and other saints, which are inserted in the last continuation of the *Bibliotheca Patrum* by Combesius.

Nicetas, Achonitates, a Greek historian of the thirteenth century, called also Choniates, from having been born at Chone, or Colossus, in Phrygia. He was employed in several considerable affairs at the court of Constantinople; and when that city was taken by the French in 1204, he withdrew, with a young French captive, whom he afterwards married at Nice, in Bithynia, where he ended his days in 1206. He wrote a History, or Annals, from the death of Alexius Comnenus in the year 1118, to that of Baldwin in 1205; a work of which we have a Latin translation by Jerome Wolf, printed at Basil in 1557, and inserted in the body of the Byzantine Historians, printed at the Louvre.

Nichols, Frank, doctor of physic, was born in London in the year 1699. His father was a barrister at law, and both his parents were of good families in Cornwall. After receiving the first rudiments of his education at a private school in the country, where his docility and sweetness of temper endeared him equally to his master and his schoolfellows, Frank was in a few years removed to Westminster, and from thence to Oxford, where he was admitted a commoner of Exeter College, under the tuition of Mr John Haviland, on the 4th of March 1714. There he applied himself diligently to all the usual academical studies, but particularly to natural philosophy and polite literature, of which the fruits were most conspicuous in his subsequent lectures on physiology. After reading a few books on anatomy, in order to perfect himself in the nomenclature of the animal parts then adopted, he engaged in dissections, and then devoted himself to the study of nature, perfectly free and unbiased by the opinions of others. When he was chosen reader of anatomy in that university, he employed his utmost attention to elevate and illustrate a science which had there been long depressed and neglected; and by quitting the beaten track of former lecturers, and minutely investigating the texture of every viscus, as well as the nature and order of every vessel, he gained a high and just reputation. He did not then reside at Oxford; but when he had finished his lectures, he used to repair to London, the place of his abode, where he had determined to settle. He had once an intention of establishing himself in Cornwall, and for a short time practised there with great reputation; but being soon tired of the fatigues attendant on that profession in the country, he returned to London, bringing back with him a great insight, acquired by diligent observation, into the nature of the miliary fever, and which was attended with the most salutary effects in his subsequent practice in the metropolis.

About this time he resolved to visit the Continent, partly with the view of acquiring a knowledge of men, manners, and languages, but chiefly to make himself acquainted with the opinions of foreign naturalists on his favourite study. At Paris, by conversing freely with the learned, he soon recommended himself to their notice and esteem. Winslow's was the only good system of physiology at that time known in France, and Morgagni's and Santorini's in Italy. On his return to England, he repeated his physiological lectures in London, which were much frequented, not only by students from both the universities, but also by many surgeons, apothecaries, and others. Soon afterwards, his new and successful treatment of the miliary fever, then very prevalent in the southern parts of England, added much to his reputation. In 1725, at a meeting of the Royal Society, he gave his opinion on the nature of aneurisms, in which he dissented from that expressed by Dr Freind in his History of Physic.

In the beginning of the year 1728, he was chosen a fellow of the Royal Society, to which he afterwards communicated the description of an uncommon disorder, namely, a polypus, resembling a branch of the pulmonary vein, for which Tulpins has strangely mistaken it, coughed up by an asthmatic person. He also made observations on a treatise, by M. Helvetius of Paris, concerning the lungs. Towards the end of the year 1729, he took the degree of doctor of physic at Oxford. On his return to London, he underwent an examination by the president and censors of the College of Physicians, previously to his being admitted a candidate, which every practitioner must be a year before he can apply to be chosen a fellow. Dr Nichols was admitted into the college on the 26th of June 1732; and two years afterwards, being chosen Gulstonian reader of Pathology, he made the structure of the heart and the circulation of the blood the subject of his lectures. In 1736, at the request of the president, he again read the Gulstonian lecture, taking for his subject those parts of the human body which serve for the secretion and discharge of the urine, with the causes, symptoms, and cure of the diseases occasioned by the stone. In 1739, he delivered the anniversary Harveian oration. In 1743, he married Elizabeth, youngest daughter of the celebrated Dr Mead, by whom he had five children, two of whom died young. In 1748, Dr Nichols undertook the office of surgical lecturer, beginning with a learned and elegant dissertation on the Anima Medica. About this time, on the death of Dr John Cunningham, one of the elects of the college, Dr Abraham Hall was, without any apparent reason, chosen to succeed him in preference to Dr Nichols, who was his senior. With a just resentment, he immediately resigned the office of surgical lecturer, and never after attended the meetings of the fellows, excepting when business of the utmost importance was in agitation. In 1751, he took some revenge in an anonymous pamphlet, entitled The Petition of the Unborn Babes to the Censors of the Royal College of Physicians of London, in which Dr Nesbit (Pocus), Dr Maule (Manlius), Dr Barrowby (Barbone) principally, and Sir William Browne, Sir Edward Hulse, and the Scotch incidentally, are the objects of his satire.

In 1753, on the death of Sir Hans Sloane in his ninety-fourth year, Dr Nichols was appointed to succeed him as one of the king's physicians, and held that office till the death of his royal master in 1760, when this skilful physician was superseded with something like the offer of a pension, which he rejected with disdain. The causes of the uncommon disorder of which George II. died, viz. a rupture of the right ventricle of the heart, he explained in a letter to the Earl of Macclesfield, president of the Royal Society, which was published in the Philosophical Transactions.

In 1772, Dr Nichols published a second edition of his treatise De Anima Medica, to which he added a dissertation De motu Cordis et Sanguinis in homine nato et non nato, inscribed to his learned friend and coadjutor Dr Lawrence.

Being at length tired of London, and also desirous of superintending the education of his son, he removed to Oxford, where he had most agreeably spent some years in his youth. But when the study of the law recalled Mr Nichols to London, he took a house at Epsom, where he passed the remainder of his life in literary retirement, not inattentive to natural philosophy, especially the cultivation of grain and the improvement of barren soils, and contemplating also with admiration the internal nature of plants, as taught by Linnæus.

His constitution never was robust. In his youth, at Oxford, he was with difficulty recovered from a dangerous fever by the skill of Drs Frampton and Frewen; and afterwards at London he had frequently been afflicted with a catarrh, and an inveterate asthmatic cough, which, returning with great violence at the beginning of the year 1778, deprived the world of this valuable man, on the 7th of January, in the eightieth year of his age.