(see Lens and Dioptries, Encycl.), are either blown or ground.

Blown Lenses are used only in the single microscope; and and the usual method of making them has been to draw out a fine thread of the soft white glass called crystal, and to convert the extremity of this into a sphere by melting it at the flame of a candle. But this glass contains lead, which is disposed to become opaque by partial reduction, unless the management be very carefully attended to. We are informed, however, by Mr Nicholson, that the hard glass used for windows seldom fails to afford excellent spheres. This glass is of a clear bright green colour when seen edgeways. A thin piece was cut from the edge of a pane of glass less than one tenth of an inch broad. This was held perpendicularly by the upper end, and the flame of a candle was directed upon it by the blow-pipe at the distance of about an inch from the lower end. The glass became soft, and the lower piece descended by its own weight to the distance of about two feet, where it remained suspended by a thin thread of glass about one five-hundredth of an inch in diameter. A part of this thread was applied edgewise to the lower-blue part of the flame of the candle without the use of the blow pipe. The extremity immediately became white hot, and formed a globule. The glass was then gradually and regularly thrust towards the flame, but never into it, until the globule was sufficiently large. A number of these were made; and being afterwards examined, by viewing their focal images with a lens magnifier, proved very bright, perfect, and round. This, as the ingenious author observes, may prove an acceptable piece of information to those eminent men (and there are many such), whose narrow circumstances, or remote situations, are obliged to have recourse to their own skill and ingenuity for experimental implements.

**Ground Lenses**, are such as are ground or rubbed into the desired shape, and then polished. Different shapes have been proposed for lenses; but in the article **Optics**, no 251 (*Encyc.*), it has been shown that, after all, the spherical is the most practically useful. By many of the methods of grinding, however, the artificer, with his utmost care, can only produce an approximation to a truly spherical figure; and, indeed, gentlemen have, for the most part, nothing to depend on for the sphericity of the lenses of their telescopes, but the care and integrity of the workmen. In the 41st volume of the Transactions of the Royal Society of London, a machine is described by Mr Samuel Jenkins, which, as it is contrived to turn a sphere at one and the same time on two axes, cutting each other at right angles, will produce the segment of a true sphere merely by turning round the wheels, and that without any care or skill in the workmen. The following description of this machine will enable our readers fully to comprehend its construction, and the mode of using it: A is a globe covered with cement, in which are fixed the pieces of glass to be ground. This globe is fastened to the axis, and turns with the wheel B. C is the brass cup which polishes the glass: this is fitted to the axis, and turns with the wheel D. The motion of the cup C, therefore, is at right angles with the motion of the globe A; whence it follows demonstrably, that the pieces of glass ground by this double motion must be formed into the segments of spheres.

**Leo X.** is a pontiff to whom learning, and art, and science, are so deeply indebted, that not to give a sketch of his life and character, in a Work of this kind, would be an unpardonable omission. A character of him is indeed given in the *Encyclopaedia*; but it is so far from the truth, that it is difficult to conceive the prejudices under which he must have laboured by whom such a label was drawn up.

Leo, whose name, before his elevation to the pontificate, was Giovanni de Medici, was the second son of Lorenzo de Medici, justly styled the Magnificent. In the life of that great man published in this Supplement, the reader will see by what means, and for what purpose, he got Giovanni raised to the dignity of cardinal at so early a period of life; and in the elegant work of Roscoe, to which we there refer, he will find such instructions of Lorenzo to the cardinal as must have made a deep impression on his youthful mind.

Speaking of his promotion, Lorenzo says, "The first thing that I would suggest to you, is, that you ought to be grateful to God, and continually to recollect that it is not through your merits, your prudence, or your solicitude, that this event has taken place, but through his favour, which you can repay only by a pious, chaste, and exemplary life; and that your obligations to the performance of these duties are so much the greater, as in your early years you have given some reasonable expectation that your riper age may produce such fruits. It would indeed be highly disgraceful, and as contrary to your duty as to my hopes, if at a time when others display a greater share of reason, and adopt a better mode of life, you should forget the precepts of your youth, and forfeit the path in which you have hitherto trodden."—"I well know (continues Lorenzo), that as you are now to reside at Rome, that sink of all iniquity, the difficulty of conducting yourself by these admonitions will be increased. The influence of example is itself prevalent; but you will probably meet with those who will particularly endeavour to corrupt and incite you to vice; because, as you yourself may perceive, your early attainment of so great a dignity is not observed without envy, and those who could not prevent your receiving that honour, will secretly endeavour to diminish it, by inducing you to forfeit the good estimation of the public."—"You are not unacquainted with the great importance of the character which you have to sustain; for you well know, that all the Curial world would prosper if the cardinals were what they ought to be; because in such a case there would always be a good pope, upon which the tranquillity of Christendom so materially depends."

As this was a confidential letter from Lorenzo to his son, the first of these extracts furnishes very sufficient evidence, that Giovanni had been at least a well behaved boy, diligent in his studies, and regular in his conduct; and without supposing him remarkably religious, the admonitions of such a father, aided by his own ambition and love of letters, would surely guard him against such gross licentiousness as that of which he is accused in the *Encyclopaedia*. How much he revered his father, is apparent from the letter which he wrote to his brother immediately after Lorenzo's death. "What a father (says he) have we lost! How indulgent to his children! Wonder not, then, that I grieve, that I lament, that I find no rest. Yet, my brother, I have some consolation in reflecting that I have thee, whom I shall always regard in the place of a father." Surely this is not the language of a grovelling flatterer, or of one who could soon forget forget the salutary admonitions of such a parent as Lorenzo de Medici. But it is needless to infer the decency of his character by such reasonings as these. The story published in the Encyclopaedia, of the manner in which the Cardinal de Medici obtained the tiara, cannot possibly be true. The reader, who shall turn to the article Pope in that Work, will find that the conclave, when fitted up for an election, is so large a place, that we may safely affirm, that had the cardinal's ulcer discharged matter so fetid as to poison all the cells, the assertion of the physicians would have been verified, and that in the then state of the healing art, the new pope could not have survived a month. Let it be remembered, too, that Leo, at his accession, was not 30, but 37 years of age, and that he had long ruled in Florence with sovereign sway by the same means which had upheld the authority of his father. The follies of youth, therefore, had he ever been remarkable for such follies, must have been over with him; and in such a state as Florence he could not have maintained the authority of Lorenzo, without exhibiting not only Lorenzo's liberality, but likewise his decency of manners.

The next charge brought against Leo in the Encyclopaedia is, that he published general indulgences throughout Europe; and this is so expressed as to lead the ill-informed reader to suppose, either that no such indulgences had ever been published by any of his predecessors, or that there was something peculiarly scandalous in Leo's mode of publishing them. Both suppositions, however, are erroneous. The historian of the council of Trent, who certainly was not partial to the court of Rome, or to the dispensing power of the pope, has shewn, that the practice of raising money by the publication of indulgences, had prevailed ever since the year 1100; that many former popes had raised money in this manner for purposes much less laudable than those which Leo had in his eye; and that the real cause of Luther's attack upon Leo's indulgences was, that they were preached through Saxony by the Dominican friars; whereas the preaching of former indulgences had been committed to the hermits of St Augustine, the order to which Luther himself belonged!

Leo is likewise accused in the Encyclopaedia of being a professed infidel, and of having called Christianity "a fable very profitable for him and his predecessors." But of the truth of this accusation there seems not to be the shadow of evidence. Leo had too much sense to utter expressions of this kind, even had he been an unbeliever in his heart; for he could not possibly expect that his indulgences and pardons would be purchased, had he declared in such strong terms that they were of no value. Father Paul indeed says, that he was not a deep divine, or so pious as some of his predecessors; but he affirms, that he adorned the papacy with many admirable qualities; that he was learned, affable, liberal, good; that he delighted in healing differences, and that his equal had not, for many years, filled the chair of St Peter. Surely this is not the character of a profane infidel!

Leo has been charged with raising his own family to grandeur at the expense of justice; and of dealing treacherously, in order to effect this purpose, both with the emperor and with the French king. But the charge is either false or greatly exaggerated. He lost no opportunity indeed of aggrandizing his relations, well knowing, that in order to secure to them any lasting benefit, it was necessary that they should be powerful enough to defend themselves, after his death, from the rapacious aims of succeeding pontiffs; but, in prosecuting this plan, he was so far from acting tyrannically or injuriously to others, that during his pontificate, the papal dominions enjoyed a degree of tranquillity superior to any other Italian state. During the contests that took place between the emperor and the French king, so far from acting treacherously, he distinguished himself by his moderation, his vigilance, and his political address; on which account he is justly celebrated by an eminent historian of our own*, as "the only prince of the age* Dr R—— who observed the motions of the two contending monarchs with a prudent attention, or who discovered a proper solicitude for the public safety."

We trust that no zealous Protestant will think we have employed our time ill, in vindicating the character of this splendid pontiff; for good learning, and, of course, true religion, are more indebted to Leo X. than to any other individual of the age in which he lived, his father Lorenzo alone excepted.

Leo Minor, the Little Lion, a constellation of the northern hemisphere, and one of the new ones that were formed out of what were left by the ancients, under the name of Stelle Informer, or unformed stars. See Astronomy, n° 456, Encycl.

Leslie (Charles), was a man so eminent for his learning, his talents, and his piety, that a fuller account of him than that which is given in the Encyclopaedia must be acceptable to our Christian readers. He was the second son of Dr John Leslie bishop of Clogher in Ireland, who was descended from an ancient family in the north of Scotland, and being an admirable scholar, rose to the dignity of bishop of Orkney, in his own country, whence he was translated, in 1633, to Raphoe in Ireland, and afterwards, in 1661, to the see of Clogher.

Our author was born in Ireland, but in what year we have not learned. A ludicrous story goes indeed of his having been begotten in prison, and of his father having said that he hoped he would in consequence become the greatest scourge of the covenanters that Great Britain or Ireland had ever seen. This story, with all its circumstances as told to us, can hardly be true; but we think it could not have been fabricated, had not Charles Leslie been born within a year of Cromwell's conquest of Ireland, when the good bishop, having sustained a siege in his castle of Raphoe against that arch rebel, was some time kept in close confinement.

We are equally ignorant of the school where he was educated as of the year of his birth; but we know that he had his academical education in Trinity College, Dublin, where he took the degree of master of arts. In the year 1671, he lost his father, when he came over to England, and, entering himself in the temple, studied law for some years, but afterwards relinquished it for the study of divinity. In 1680, he was admitted into holy orders; and, in 1687, was made chancellor of Connor.

About this period he rendered himself particularly obnoxious to the Popish party in Ireland, by his zealous opposition to them, which was thus called forth. Roger Boyle, bishop of Clogher, dying in 1687, Patrick Tyrrel was made titular Popish bishop, and had the revenues of the see assigned him by king James. He set up a convent of friars in Monaghan; and, fixing his habitation there, held a public visitation of his clergy with great solemnity; when, some subtle logicians attending him, he was so insolent as to challenge the Protestant clergy to a public disputation. Leslie undertook the task, and performed it to the satisfaction of the Protestants; though it happened, as it generally does at such contests, that both sides claimed the victory. He afterwards held another public disputation with two celebrated Popish divines, in the church of Tynan, in the diocese of Armagh, before a very numerous assembly of persons of both religions; the issue of which was, that Mr John Stewart, a Popish gentleman, solemnly renounced the errors of the church of Rome.

As the Papists had got possession of an Episcopal see, they engrossed other offices too; and a Popish high-sheriff was appointed for the county of Monaghan. This proceeding alarmed the gentlemen in that county; who, depending much on Leslie's knowledge as a justice of peace, repaired to him, then confined, by the court, to his house. He told them, that it would be as illegal in them to permit the sheriff to act as it would be in him to attempt it. But they insisting that he should appear himself on the bench at the next quarter-sessions, and all promising to stand by him, he was carried thither with much difficulty and in great pain. When the sheriff appeared, and was taking his place, he was asked whether he was legally qualified; to which he answered pertly, "That he was of the king's own religion, and it was his majesty's will that he should be sheriff." Leslie replied, "That they were not inquiring into his majesty's religion, but whether he (the pretended sheriff) had qualified himself according to law, for acting as a proper officer; that the law was the king's will, and nothing else to be deemed such; that his subjects had no other way of knowing his will, but as it is revealed to them in his laws; and it must always be thought to continue so, till the contrary is notified to them in the same authentic manner." Upon this, the bench unanimously agreed to commit the pretended sheriff, for his intrusion and arrogant contempt of the court. Leslie also committed some officers of that tumultuous army which the Lord Tyrconnell raised for robbing the country.

In this spirited conduct Leslie acted like a sound divine and an upright magistrate; but though he thought himself authorized to refuse the illegal mandates of his sovereign, like many other great and good men, he distinguished between active and passive obedience, and felt not himself at liberty to transfer his allegiance from that sovereign to another. Refusing therefore to take the oath to king William and queen Mary, he was deprived of all his preferments; and in 1689 he removed with his family to England, where he published the following works, besides those already noticed in the Encyclopedia:

1. Answer to Archbishop King's State of the Protestants in Ireland. 2. Cassandra, concerning the new Associations, &c., 1703, 4to. 3. Rehearsals; at first a weekly paper, published afterwards twice a week in a half-sheet, by way of dialogue on the affairs of the times; begun in 1704, and continued for five or seven years. 4. The Wolf stripped of his Shepherd's Clothing, in Answer to Moderation a Virtue, 1704, 4to. The pamphlet it answers was written by James Owen. 5. The Bishop of Sarum's [Burnet's] proper Defence, from a Speech said to be spoken by him against occasional conformity, 1704, 4to. 6. The new Association of those called Moderate Churchmen, &c., occasioned by a pamphlet, intitled, The Danger of Priestcraft, 1705, 4to. 7. The new Association, part 2d, 1705, 4to. 8. The Principles of Dissenters concerning Toleration and occasional Conformity, 1705, 4to. 9. A Warning for the Church of England, 1706, 4to. Some have doubted whether these two pieces were his. 10. The good old Cause, or Lying in Truth; being a second Defence of the Bishop of Sarum from a second Speech, &c., 1710. For this warrant was issued out against Leslie. 11. A Letter to the Bishop of Sarum, in Answer to his Sermon after the Queen's Death, in Defence of the Revolution, 1715. 12. Salt for the Leech. 13. The Anatomy of a Jacobite. 14. Galileans redivivus. 15. Delenda Carthago. 16. A Letter to Mr William Molyneux, on his Case of Ireland's being bound by the English Acts of Parliament. 17. A Letter to Julian Johnson. 18. Several Tracts against Dr Hyden and Mr Hoadly. 19. A Discourse, shewing who they are that are now qualified to administer Baptism. 20. The History of Sin and Heresy, &c., 1698, 8vo. 21. The Truth of Christianity demonstrated, in a Dialogue between a Christian and a Deist, 1711, 8vo.—Against the Papists. 22. Of private Judgment and Authority in Matters of Faith. 23. The Case stated between the Church of Rome and the Church of England, &c., 1713. 24. The true notion of the Catholic Church, in Answer to the Bishop of Meaux's Letter to Mr Nelson, &c.

Besides these, he published the four following tracts: 25. A Sermon preached in Chester, against Marriages in different Communions, 1702, 8vo. This sermon occasioned Mr Dodwell's discourse upon the same subject. 26. A Dissertation concerning the Use and Authority of Ecclesiastical History. 27. The Case of the Regal and the Pontificate. 28. A Supplement, in Answer to a Book, intitled, The regal Supremacy in Ecclesiastical Affairs asserted, &c. These two last pieces were occasioned by the dispute about the rights of convocation, between Wake, &c. on one side, and Atterbury and his friends, among whom was Leslie, on the other.

It is said by the authors of the Biographical Dictionary, that, in consequence of a publication of his, intitled, "The hereditary right of the crown of England affected," he was under the necessity of leaving the kingdom; and that he repaired to the Pretender at Bar le duc, where he was allowed to officiate, in a private chapel, after the rites of the church of England; and where he endeavoured, though in vain, to convert the Pretender to the Protestant religion.

That he repaired to Bar le duc, and endeavoured to convert to the church of England him whom he considered as the rightful sovereign of England, is indeed true; but we have reason to believe that this was not in consequence of his being obliged to leave the kingdom. There is, in the first place, some grounds to believe, that "The hereditary right of the crown of England affected" was not written by him; and there is still in existence undoubted evidence, that, in consequence of his great fame as a polemic, he was sent to Bar le duc for the express purpose of endeavouring to convert the son of James II. by some gentlemen of fortune in England, who wished to see that prince on the throne of of his ancestors. The writer of this article had the honour, 16 or 17 years ago, to be known to the grand- daughter of one of those gentlemen—a lady of the strictest veracity; and from her he received many anecdotes of Leslie and his associates, which, as he did not then foresee that he should have the present occasion for them, he has suffered to slip from his memory. That lady is still alive, and we have reason to believe is in possession of many letters by Leslie, written in confidence to her grandfather; both from Bar le duc and from St Germain; and by the account which she gave of these letters, Leslie appears to have considered his prince as a weak and incorrigible bigot, though, in every thing but religion, an amiable and accomplished man. This may have been his genuine character; for we all know that it was the character of his father; but it is not of him that we are writing.

Mr Leslie having remained abroad from the year 1709 till 1721, returned that year to England, resolving, whatever the consequences might be, to die in his own country. Some of his friends acquainting lord Sunderland with his purposes, implored his protection for the good old man, which his lordship readily and generously promised. Mr Leslie had no sooner arrived in London, than a member of the house of commons officially waited on lord Sunderland with the news, but met with such a reception from his lordship as the malice of his errand deserved. Our author then went over to Ireland, where he died April 13, 1722, at his own house at Glanough in the county of Monaghan.

His character may be summed up in a few words. Consummate learning, attended by the lowest humility, the strictest piety without the least tincture of moroseness, a conversation to the last degree lively and spirited, yet to the last degree innocent, made him the delight of mankind, and leaves what Dr Hickes says of him unquestionable, that he made more converts to a sound faith and holy life than any other man of our times.

A charge, however, has been lately brought against him of such a nature, as, if well founded, must detract not only from his literary fame, but also from his integrity. "The short and easy Method with the Deists" is unquestionably his most valuable, and apparently his most original work; yet this tract is published in French among the works of the Abbé St Real, who died in 1692; and therefore it has been said, that unless it was published in English prior to that period, Charles Leslie must be considered as a shameless plagiarist.

The English work was certainly not published prior to the death of Abbé St Real; for the first edition bears date July 17th 1697; and yet many reasons conspire to convince us, that our countryman was no plagiarist. There is indeed a striking similarity between the English and the French works; but this is no complete proof that the one was copied from the other. The article Philology in the Encyclopaedia Britannica, of which Dr Doig is the author, was published the very same week with Dr Vincent's dissertation on the Greek verb. It was therefore impossible that either of these learned men, who were till then strangers to each other's names, could have stolen aught from the other; and yet Dr Vincent's derivation of the Greek verb bears as striking a resemblance to Dr Doig's as the Abbé St Real's work does to Charles Leslie's. In the article Miracle (Encyc.), the credibility of the gospel miracles is established by an argument, which the author certainly borrowed from no man, and which the late principal Campbell considered as original; yet within half a year of the publication of that article, the credibility of the gospel miracles was treated in the very same manner by P. Sayers, M. D.; though there is in his dissertation complete internal evidence that he had not seen the article in the Encyclopedia. Not many months ago, the author of this sketch reviewed, in one of the journals, the work of a friend, which was at the same time reviewed in another journal, that at this moment he has never seen. Yet he has been told by a friend, who is much versed in that kind of reading, and knows nothing of his concern with either review, that the book in question must, in both journals, have been reviewed by the same hand; because in both the same character is given of it in almost the very same words!

After these instances of apparent plagiarism, which we know to be only apparent, has any man a right to say that Charles Leslie and the Abbé St Real might not have treated their subject in the way that they have done, without either borrowing from the other? The coincidence of arrangement and reasoning in the two works is indeed very surprising; but it is by no means so surprising as the coincidence of etymological deductions which appears in the works of the Doctors Doig and Vincent. The divines reason from the acknowledged laws of human thought; the reasonings of the grammarians, with all due deference to their superior learning, we cannot help considering as sometimes fanciful.

But this is not all that we have to urge on the subject. If there be plagiarism in the case, and the identity of titles looks very like it, it is infinitely more probable that the editor of St Real's works stole from Leslie, than that Leslie stole from St Real, unless it can be proved that the works of the Abbé, and this work in particular, were published before the year 1697. At that period, the English language was very little read or understood on the continent; whilst in Britain the French language was, by scholars, as generally understood as at present. Hence it is, that so many Frenchmen, and indeed foreigners of different nations, thought themselves safe in pilfering science from the British philosophers; whereas there is not, that we know, one well authenticated instance of a British philosopher appropriating to himself the discoveries of a foreigner. If, then, such men as Leibnitz, John Bernoulli, and Des Cartes, trusting to the improbability of detection, condescended to pilfer the discoveries of Hooke, Newton, and Harriot, is it improbable that the editor of the works of St Real would claim to his friend a celebrated tract, of which he knew the real author to be obnoxious to the government of his own country, and therefore not likely to have powerful friends to maintain his right?

But farther, Burnet, bishop of Sarum, was an excellent scholar, and well read, as every one knows, in the works of foreign divines. Is it conceivable, that this prelate, when residing under the lath of Leslie, would have let slip to good an opportunity of covering with disgrace his most formidable antagonist, had he known that antagonist to be guilty of plagiarism from the writings of the Abbé St Real? Let it be granted, however, however, that Burnet was a stranger to these writings and to this plagiarism; it can hardly be supposed that Le Clare was a stranger to them likewise. Yet this author, when, for reasons best known to himself, he chose (1706) to depreciate the argument of the short method, and to traduce its author as ignorant of ancient history, and as having brought forward his four marks for no other purpose than to put the deceitful traditions of Popery on the same footing with the most authentic doctrines of the gospel, does not so much as insinuate that he borrowed these marks from a Popish abbe, though such a charge, could he have established it, would have served his purpose more than all his rude railings and invective. But there was no room for such a charge.

In the second volume of the works of St Real, published in 1757, there is indeed a tract entitled Méthode Courte et Affic pour combattre les Défis; and there can be little doubt but that the publisher wished it to be considered as the work of his countryman. Unfortunately, however, for his design, a catalogue of the Abbe's works is given in the first volume; and in that catalogue the Méthode Courte et Affic is not mentioned.

We have dwelt thus long on The Short and Easy Method with the Deists, because it is one of the ablest works that ever was written in proof of the Divine origin of the Jewish and Christian Scriptures; a work of which the merit is acknowledged by Lord Bolingbroke, and which, as has been observed elsewhere (see Theology, n° 16, Encycl.) Dr Conyers Middleton confesses to be unanswerable. If by men of science we be thought to have spent our time well in vindicating the rights of our illustrious philosophers Hooke and Newton, to discoveries which have been unjustly claimed by the philosophers of Germany and France; we will not fairly by the friends of Christianity be thought to have employed our time ill in vindicating Leslie's claim to this decisive argument in support of our holy religion.