EUCLID, Greek mathematician of the 3rd century B.C.; we are ignorant not only of the dates of his birth and death, but also of his parentage, his teachers, and the residence of his early years. In some of the editions of his works he is called Megarensis, as if he had been born at Megara in Greece, a mistake which arose from confounding him with another Euclid, a disciple of Socrates. Proclus (A.D. 412485), the authority for most of our information regarding Euclid, states in his commentary on the first book of the Elements that Euclid lived in the time of Ptolemy I., king of Egypt, who reigned from 323 to 285 B.C., that he was younger than the associates of Plato, but older than Eratosthenes (276–196 B.C.) and Archimedes (287–212 B.C.). Euclid is said to have founded the mathematical school of Alexandria, which was at that time becoming a centre, not only of commerce, but of learning and research, and for this service to the cause of exact science he would have deserved commemoration, even if his writings had not secured him a worthier title to fame. Proclus preserves a reply made by Euclid to King Ptolemy, who asked whether he could not learn geometry more easily than by studying the Elements—" There is no royal road to geometry." Pappus of Alexandria, in his Mathematical Collection, says that Euclid was a man of mild and inoffensive temperament, unpretending, and kind to all genuine students of mathematics. This being all that is known of the life and character of Euclid, it only remains therefore to speak of his works.
Among those which have come down to us the most remarkable is the Elements (ErosxeIa) (see GEOMETRY). They consist of thirteen books; two more are frequently added, but there is reason to believe that they are the work of a later mathematician, Hypsicles of Alexandria.
The question has often been mooted, to what extent Euclid, in his Elements, is a discoverer or a compiler. To this question no entirely satisfactory answer can be given, for scarcely any of the writings of earlier geometers have come down to our times. We are mainly dependent on Pappus and Proclus for the scanty notices we have of Euclid's predecessors, and of the problems which engaged their attention; for the solution of problems, and not the discovery of theorems, would seem to have been their principal object. From these authors we learn that the property of the rightangled triangle had been found out, the principles of geometrical analysis laid down, the restriction of constructions in plane geometry to the straight line and the circle agreed upon, the doctrine of proportion, for both commensurables and incommensurables, as well as loci, plane and solid, and some of the properties of the conic sections investigated, the five regular solids (often called the Platonic bodies) and the relation between the volume of a cone or pyramid and that of its circumscribed cylinder or prism discovered. Elementary works had beenwritten, and the famous problem of the duplication of the cube reduced to the determination of two mean proportionals between two given straight lines. Notwithstanding this amount of discovery, and all that it implied, Euclid must have made a great advance beyond his predecessors (we are told that " he arranged the discoveries of Eudoxus, perfected those of Theaetetus, and reduced to invincible demonstration many things that had previously been more loosely proved "), for his Elements supplanted all similar treatises, and, as Apollonius received the title of " the great geometer," so Euclid has come down to later ages as the elementator."
For the past twenty centuries parts of the Elements, notably the first six books, have been used as an introduction to geometry. Though they are now to some extent superseded in most countries, their long retention is a proof that they were, at any rate, not unsuitable for such a purpose. They are, speaking generally, not too difficult for novices in the science; the demonstrations are rigorous, ingenious and often elegant; the mixture of problems and theorems gives perhaps some variety, and makes their study less monotonous; and, if regard be had merely to the metrical properties of space as distinguished from the graphical, hardly any cardinal geometrical truths are omitted. With these excellences are combined a good many defects, some of them inevitable to a system based on a very few axioms and postulates. Thus the arrangement of the propositions seems arbitrary; associated theorems and problems are not grouped together; the classification, in short, is imperfect. Other objections, not to mention minor blemishes, are the prolixity of the style, arising partly from a defective nomenclature, the treatment of parallels depending on an axiom which is not axiomatic, and the sparing use of superposition as a method of proof.
Of the thirtythree ancient books subservient to geometrical analysis, Pappus enumerates first the Data (Deboje a) of Euclid. He says it contained 90 propositions, the scope of which he describes; it now consists of 95. It is not easy to explain this discrepancy, unless we suppose that some of the propositions, as they existed in the time of Pappus., have since been split into two, or that what were once scholia have since been erected into propositions. The object of the Data is to show that when certain things—lines, angles, spaces, ratios, &c.—are given by hypothesis, certain other things are given, that is, are determinable. The book, as we are expressly told, and as we mdy gather from its contents, was intended for the investigation of problems; and it has been conjectured that Euclid must have extended the method of the Data to the investigation of theorems. What prompts this conjecture is the similarity between the analysis of a theorem and the method, common enough in the Elements, of reductio ad absurdum—the one setting out from the supposition that the theorem is true, the other from the supposition that it is false, thence in both cases deducing a chain of consequences which ends in a conclusion previously known to be true or false.
The Introduction to Harmony (Elaaycayil ap/.iOV HOD, and the Section of the Scale (Kararo,uh Kavovos), treat of music. There is good reason for believing that one at any rate, and probably both, of these books are not by Euclid. No mention is made of them by any writer previous to Ptolemy (A.D. 140), or by Ptolemy himself, and in no ancient codex are they ascribed to Euclid.
The Phaenomena (cawoµeva) contains an exposition of the appearances produced by the motion attributed to the celestial sphere. Pappus, in the few remarks prefatory to his sixth book. complains of the faults, both of omission and commission, of writers on astronomy, and cites as an example of the former the second theorem of Euclid's Phaenomena, whence, and from the interpolation of other proofs, David Gregory infers that this treatise is corrupt.
The Optics and Catoptrics ('Oirruua, KaroirrpuKh) are ascribed to Euclid by Proclus, and by Marinus in his preface to the Data, but no mention is made of them by Pappus. This latter circumstance, taken in connexion with the fact that two of the propositions in the sixth book of the Mathematical Collection prove the
same things as three in the Optics, is one of the reasons given by Gregory for deeming that work spurious. Several other reasons will be found in Gregory's preface to his edition of Euclid's works.
In some editions of Euclid's works there is given a book on the Divisions of Superficies, which consists of a few propositions, showing how a straight line may be drawn to divide in a given ratio triangles, quadrilaterals and pentagons. This was supposed by John Dee of London, who transcribed or translated it, and entrusted it for publication to his friend Federico Commandino of Urbino, to be the treatise of Euclid referred to by Proclus as Tb aepi &aip&r wv (3g3Xlov. Dee mentions that, in the copy from which he wrote, the book was ascribed to Machomet of Bagdad, and adduces two or three reasons for thinking it to be Euclid's. This opinion, however, he does not seem to have held very strongly, nor does it appear that it was adopted by Commandino. The book does not exist in Greek.
The fragment, in Latin, De levi et ponderoso, which is of no value, and was printed at the end of Gregory's edition only in order that nothing might be left out, is mentioned neither by Pappus nor Proclus, and occurs first in Bartholomew Zamberti's edition of 1537. There is no reason for supposing it to be genuine.
The following works attributed to Euclid are not now extant:
1. Three books on Porisms (Hepi Twv Tropes shrwv) are mentioned both by Pappus and Proclus, and the former gives an abstract of them, with the lemmas assumed. (See PoRISM.)
2. Two books are mentioned, named T&&rwv srpbs irt0avei¢; which is rendered Locorum ad supericiem by Commandino and subsequent geometers. These books were subservient to the analysis of loci, but the four lemmas which refer to them and which occur at the end of the seventh book of the Mathematicab Collection, throw very little light on their contents. R. Simson's opinion was that they treated of curves of double curvature, and he intended at one time to write a treatise on the subject. (See Trail's Life of Dr Simson).
3. Pappus says that Euclid wrote four books on the Conic Sections (f3tAi.a rkaapa KWVCK&JV), which Apollonius amplified, and to which he added four more. It is known that, in the time of Euclid, the parabola was considered as the section of a rightangled cone, the ellipse that of an acuteangled cone, the hyperbola that of an obtuseangled cone, and that Apollonius was the first who showed that the three sections could be obtained from any cone. There is good ground therefore for supposing that the first four books of Apollonius's Conics, which are still extant, resemble Euclid's Conics even less than Euclid's Elements do those of Eudoxus and Theaetetus.
4. A book on Fallacies (Hepi 1/ev&apiwv) is mentioned by Proclus, who says that Euclid wrote it for the purpose of exercising beginners in the detection of errors in reasoning.
This notice of Euclid would be incomplete without some account of the earliest and the most important editions of his works. Passing over the commentators of the Alexandrian school, the 'first European translator of any part of Euclid is Boetius (500), author of the De consolatione philosophiae. His Euclidis Megarensis geometriae libri duo contain nearly all the definitions of the first three books of the Elements, the postulates, and most of the axioms. The enunciations, with diagrams but no proofs, are given of most of the propositions in the first, second and fourth books, and a few from the third. Some centuries afterwards, Euclid was translated into Arabic, but the only printed version in that language is the one made of the thirteen books of the Elements by Nasir AIDin AlTusi (13th century), which appeared at Rome in 1594.
The first printed edition of Euclid was a translation of the fifteen books of the Elements from the Arabic, made, it is supposed, by Adelard of Bath (12th century), with the comments of Campanus of Novara. It appeared at Venice in 1482, printed by Erhardus Ratdolt, and dedicated to the doge Giovanni Mocenigo. This edition represents Euclid very inadequately; the comments are often foolish, propositions are sometimes omitted, sometimes joined together, useless cases are interpolated, and now and then Euclid's order changed.
The first printed translation from the Greek is that of Bartholomew Zamberti, which appeared at Venice in 1505. Its contents will be seen from the title: Euclidis megaresis philosophi platonici Mathematicaru3 disciplinaru Janitoris: Habent in hoc volumine quicugg ad mathematic¢ substantici aspir¢t: elemetorum libros xiii cu expositione Theonis insignis mathematici . Quibus . adjuneta. Deputatum scilicet Euclidi volume xiiii cu expositioe Hypsi.
Alex. Itideg3 Phaeno. Specu. Perspe. cum expositione Theonis ac mirandus ille liber Datorum cum expositioe Pappi Mechanici una cu Marini dialectici protheoria. Bar. Zaber. Vene. Interpte.
The first printed Greek text was published at Basel, in 1533, with
the title EUKXei8ov ITOLxE7.W1, /3113X. LE K TWV OEWVOS O•VVOVQLWV. It
was edited by Simon Grynaeus from two MSS. sent to him, the one from Venice by Lazarus Bayfius, and the other from Paris by
John Ruellius. The four books of Proclus's commentary are given at the end from an Oxford MS. supplied by John Claymundus. The English edition, the only one which contains all the extant works attributed to Euclid, is that of Dr David Gregory, published at Oxford in 1703, with the title, EUKXeteov Td owj'6µeva. Euclidis quae supersunt omnia. The text is that of the Basel edition, corrected from the MSS. bequeathed by Sir Henry Savile, and from Savile's annotations on his own copy. The Latin translation, which accompanies the Greek on the same page, is for the most part that of Commandino. The French edition has the title, Les fEuvres d'Euclide, traduites en Latin et en Francois, d'apres un manuscrit tresancien qui etait reste inconnu jusqu'd•nos jours. Par F. Peyrard, Traducleur des Leuvres d'Archimede. It was published at Paris in three volumes, the first of which appeared in 1814, the second in 1816 and the third in 1818. It contains the Elements and the Data, which are, says the editor, certainly the only works which remain to us of this evercelebrated geometer. The texts of the Basel and Oxford editions were collated with 23 MSS., one of which belonged to the library of the Vatican, but had been sent to Paris by the comte de Peluse (Monge). The Vatican MS. was supposed to date from the 9th century; and to its readings Peyrard gave the greatest weight. What may be called the German edition has the title EUKXEteov Erolxeia. Euclidis Elementa ex optimis libris in usum Tironum Graece edita ab Ernesto Ferdinando August. It was published at Berlin in two parts, the first of which appeared in 1826 and the second in 1829. The above mentioned texts were collated with three other MSS. Modern standard editions are by,Dr Heiberg of Copenhagen, Euclidis Elementa, edidit et Latine interpretatus est J. L. Heiberg. vols. i.v. (Lipsiae, 18831888), and by T. L. Heath, The Thirteen Books of Euclid's Elements, vols. i.iii. (Cambridge, 1908). Of translations of the Elements into modern languages the number is very large. The first English translation, published at London in 1570, has the title, The Elements of Geometrie of the most auncient Philosopher Euclide of Megara. Faithfully (now first) translated into the Englishe toung, by H. Billingsley, Citizen of London. Whereunto are annexed certain Scholies, Annotations and Inventions, of the best Mathematiciens, both of time past and in this our age. The first French translation of the whole of the Elements has the title, Les Quinze Livres des Elements d'Euclide. Traduicts de Latin en Francois. Par D. Henrion, Mathematicien. The first edition of it was published at Paris in 1615, and a second, corrected and augmented, in 1623. Pierre Forcadel de Bezies had published at Paris in 1564 a translation of the first six books of the Elements, and in 1565 of the seventh, eighth and ninth books. An Italian translation, with the title, Euclide Megarense acutissimo philosopho solo introduttore delle Scientie Mathematice. Diligentemente rassettato, et ally integrity ridotto, per it degno professore di tai Scientie Nicol() Tartalea Brisciano, was published at Venice in 1569, and Federico Commandino's translation appeared at Urbino in 1575; a Spanish version, Los Seis Libros primeros de la geometria de Euclides. Traduzidos en legua Espanola por Rodrigo Camorano, Astrologo y Mathematico, at Seville in 1576; and a Turkish one, translated from the edition of J. Bonnycastle by Husain Rifki, at Bulak in 1825. Dr Robert Simson's editions of the first six and the eleventh and twelfth books of the Elements, and of the Data.
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