RIEMANN Geoeg Feiedeich Beenhaed (1826-1866), mathematician, was born on the 17th September 1826, at Breselenz, near Dannenberg in Hanover. His father Friedrich Bernhard Riemann came from Mecklenburg, had served in the war of freedom, and had finally settled as pastor in Quickborn. Here with his five brothers and sisters Riemann spent his boyhood and received, chiefly from his father, the elements of his education. He showed at an early age well-marked mathematical powers, and his progress was so rapid in arithmetic and geometry that he was soon beyond the guidance not only of his father but of schoolmaster Schulz, who assisted in the mathematical department of his training....
In 1840 he went to live with his grandmother at Hanover, where he attended the lyceum. After her death, two years later, he entered the Johanneum at Lüneburg, where he finished in four years more his gymnasial education. Notwithstanding some disadvantages due to defects in his earlier training, and more particularly to shyness arising from his rustic upbringing, he speedily distinguished himself in all the branches of the gymnasial course, and was already known by the school authorities as a mathematician of great promise. The director, Schmalfuss, encouraged him in his mathematical studies by lending him books (among them Euler’s works and Legendre’s Theory of Numbers), and readily understood that he had no ordinary schoolboy to deal with when he found that works of such profoundity were read, mastered, and returned within a few days. In 1846, in his twentieth year, Riemann entered himself as a student of philology and theology in the university of Gottingen. This choice of a university career was dictated more by the natural desire of his father to see his son enter his own profession, and by the poverty of his family, which rendered the speedy earning of his living a matter of importance, than by his own preference. He sacrificed so far to the bent of his genius as to attend lectures on the numerical solution of equations and on definite integrals by Stern, on terrestrial magnetism by Goldschmidt, and on the method of least squares by Gauss. It soon became evident that his mathematical studies, undertaken at first probably as a relaxation, were destined to be the chief business of his life; and he obtained his father’s permission to devote himself entirely to a scientific career. By this time he had exhausted the resources of Göttingen in the shape of mathematical lectures; and he proceeded in the beginning of 1847 to Berlin, attracted thither by that brilliant constellation of mathematical genius whose principal stars were Dirichlet, Jacobi, Steiner, and Eisenstein. He appears to have attended Dirichlet’s lectures on theory of numbers, theory of definite integrals, and partial differential equations, and Jacobi’s on analytical mechanics and higher algebra. It was during this period that he first formed those ideas on the theory of functions of a complex variable which led to most of his great discoveries. One stirring social incident at least marked this part of his life, for, during the revolutionary insurrection in March 1848, the young mathematician, as a member of a company of student volunteers, kept guard in the royal palace from 9 o’clock on the morning of the 24th March till 1 o’clock on the afternoon of the following day.
In 1850 he returned to Göttingen and began to prepare his doctor’s dissertation, busying himself meanwhile with “Naturphilosophie” and experimental physics. In pursuit of the latter he entered the mathematical and physical seminary, then newly started by Weber, Ulrich, Stern, and Listing. This double cultivation of his scientific powers, doubtless due more to the influence of Göttingen as represented by Gauss than to Berlin, had the happiest effect on his subsequent work; for the greatest achieve; ments of Riemann were effected by the application in pure mathematics generally of a method (theory of potential) which had up to this time been used solely in the solution of certain problems that arise in mathematical physics.
In November 1851 he obtained his doctorate, the thesis being “Grundlagen für eine allgemeine Theorie der Functionen einer veränderlichen complexen Grösse.” This memoir excited the admiration of Gauss, and at once marked its author’s rank as a mathematician. The fundamental method of research which Riemann employed has just been alluded to; the results will be best indicated in his own words :—
“The methods in use hitherto for treating functions of a complex variable always started from an expression for the function as its definition, whereby its value was given for every value of the argument; by our investigation it has been shown that, in consequence of the general character of a function of a complex variable, in a definition of this sort one part of the determining conditions is a consequence of the rest, and the extent of the determining conditions has been reduced to what is necessary to effect the determination. This essentially simplifies the treatment of such functions. Hitherto, in order to prove the equality of two expressions for the same function, it was necessary to transform the one into the other, i. e., to show that both expressions agreed for every value of the variable; now it is sufficient to prove their agreement to a far less extent” [merely in certain critical points and at certain boundaries].
The time between his promotion to the doctorate and his habilitation as privat-docent was occupied by researches undertaken for his Habilitationsschrift, by “Naturphilosophie,” and by experimental work partly as Weber’s assistant in the mathematical physical seminary, and partly as collaborateur with Weber and Kohlrausch in special researches on electricity. In connexion with the results of Kohlrausch regarding the residual discharge of condensers, Riemann worked out a theory of this phenomenon which he intended to have published in Poggen-dorff ’ s Annalen. For some reason not fully explained it was not published at all during his lifetime, and its place in the Annalen was taken by an elegant little paper on Nobili’s rings.
The subject he had chosen for his Habilitationsschrift was the “Representation of a Function by means of a Trigonometrical Series,” a subject which Dirichlet had made his own by a now well-known series of researches. It was fortunate no doubt for Riemann that he had the kind advice and encouragement of Dirichlet himself, who was then on a visit at Göttingen during the preparation of his essay; but the result λvas a memoir of such originality and refinement as showed that the pupil was fully the equal of the master. Of the customary three themes which lie suggested for his trial lecture, that “On the Hypotheses which form the Foundation of Geometry” was chosen at the instance of Gauss, who was curious to hear what so young a man had to say on this difficult subject, on which he himself had in private speculated so profoundly (see Parallels, vol. xviii. p. 254). Dedekind tells us that Riemann’s lecture, which surpassed his utmost expectation, filled him with the greatest astonishment, and that on the way back from the faculty meeting he spoke to Wilhelm Weber with the highest appreciation, and with an excitement rare with him, regarding the depth of the thoughts to which Riemann had given utterance.
In 1855 Gauss died and was succeeded by Dirichlet, who along with others made an effort to obtain Riemann’s nomination as extraordinary professor. In this they were not successful; but a Government Stipendium of 200 thalers was given him, and even this miserable pittance was of great importance, so straitened were his circumstances. But this small beginning of good fortune was embittered by the deaths of his father and his eldest sister, and by the breaking up of the home at Quickborn, where he had so often found solace when ill and dejected. Meantime he was lecturing and writing the great memoir (Borchardtfi Journal, vol. liv., 1857) in which he applied the theory developed in his doctor’s dissertation to the Abelian functions. It is amusing to find him speaking jubilantly of the unexpectedly large audience of eight which assembled to hear his first lecture (in 1854) on partial differential equations and their application to physical problems. The rustic shyness which had troubled his schoolboyhood seems still to have haunted him; for he says, speaking of these lectures, “The nervousness which I had at first has pretty well subsided, and I accustom myself to think more of my hearers than of myself, and to read in their faces whether I may go on, or whether the matter requires further explanation.”
Riemann’s health had never been strong. Even in his boyhood he had shown symptoms of consumption, the disease that was working such havoc in his family; and now under the strain of work he broke down altogether, and had to retire to the Harz with his friends Ritter and Dedekind, where he gave himself up to excursions and “Naturphilosophie.” After his return to Göttingen (November 1857) he was made extraordinary professor, and his salary raised to three hundred thalers. As usual with him, misfortune followed close behind; for he lost in quick succession his brother Wilhelm and another sister. In 1859 he lost his friend Dirichlet; but his reputation was now so well established that he was at once appointed to succeed him. It now seemed for a little as if the world was to go smoothly with him. Well-merited honours began to reach him; and in 1860 he visited Paris, and met with a warm reception there. He married, and married happily, Fräulein Elise Koch in June 1862, but the following month he had an attack of pleurisy which proved the beginning of a long illness that ended only with his death. His physician recommended a sojourn in Italy, for the benefit of his health, and Weber and Sartorius von Waltershausen obtained from the Government leave of absence and means to defray the cost of the journey. At first it seemed that he would recover; but on his return in June 1863 he caught cold on the Splügen Pass, and in August of the same year had to go back to Italy. In November 1865 he returned again to Göttingen, but, although he was able to live through the winter, and even to work a few hours every day, it became clear to his friends, and clearest of all to himself, that he was dying. He was very desirous to finish some of the many investigations which had presented themselves to him, and eagerly asked his doctors to tell him how long he might reasonably expect to live, so that he might take up what he had most chance of finishing. In order to husband his few remaining days he resolved in June 1866 to return once more to Italy. Thither he journeyed through the confusion of the first days of the Austro-Prussian war, and settled in a villa at Selasca near Intra on Lago Maggiore. Here his strength rapidly ebbed away, but his mental faculties remained brilliant to the last. On the 19th of July 1866, attended by his wife, he lay under a fig-tree greatly enjoying the beautiful landscape and working at his last unfinished investigation on the mechanism of the ear. The day following he died.
There are few more pathetic stories than the life of Riemann, few finer instances of victory gained by inborn genius over a host of adverse circumstances. Few as were the years of work allotted to him, and few as are the printed pages covered by the record of his researches, his name is, and will remain, a household word among mathematicians. Most of his memoirs are masterpieces—full of original methods, profound ideas, and far-reaching imagination. Few sources, we imagine, have been fuller of inspiration for the younger mathematicians of our day than the octavo volume of five hundred pages or so that contains his works; and many an advance in mathematical science will yet be made, with increase of reputation to the maker, by carrying out his suggestions.
The collected works of Riemann were published by IL Weber assisted by R. Dedekind (8vo, Leipsic, 1876). At the end of this volume there is a touching account of his life by the latter, from which the above sketch is almost entirely taken.
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RIENZI Cola di (1313-1354). See Rome.
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RIESENER Jean Henri (1725-1806), the celebrated cabinet-maker of Louis XVI., was born at Gladbeck near Cologne in 1725. He was employed by Jean François Oeben in the arsenal, and in 1769 married Oeben’s widow, by whom he had one son. A number of fine examples of Riesener’s cabinets are described in the catalogue of furniture in the South Kensington Museum. He employed tulip, rosewood, holly, maple, laburnum, and purple wood in their construction. Wreaths and bunches of flowers form the centres of his panels; on the sides are diaper patterns in quiet colours. The name of Riesener is stamped sometimes on the panel itself, sometimes on the oak lining of the furniture made by him. The best pieces at the South Kensington Museum are from the collection of Sir Richard Wallace; perhaps the most remarkable is the bureau made for Stanislaus, king of Poland, which is signed by the maker, as is also a similar piece in the Louvre which is accompanied by gilt bronze candle branches by Gouthière. This last work, which bears the date 1769, it is believed that Riesener only finished; and indeed towards the close of his life, after his second marriage (1782) to Marie A. C. Grezel (from whom he was divorced), he ceased to produce anything, and became a collector, buying up his own works. He died January 6, 1806. His son, Henri François (1767-1828), was one of the most noted portrait-painters of the first empire. The portrait of M. Ravrio, a worker in bronze (Louvre), is a good example of his talent.
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RIESENGEBIRGE (Bohemian Krkonose), or Giant Mountains, a lofty and rugged group on the common boundary of Silesia and Bohemia, between the upper courses of the Elbe and the Oder. They form the highest portion of the Sudetic system, which separates south-east Prussia from the Austrian empire, and finds its natural continuation towards the north-west in the Erzgebirge, the Thuringian Forest, and the Harz Mountains. Adjoining the Isergebirge and the Lausitzergebirge on the west, and the Eulengebirge and the Adlergebirge on the east and south-east, the Riesengebirge proper run south-east and north-west between the sources of the Zacken and the Bober, for a distance of 23 miles, with a breadth of 14 miles. They cover an area of about 425 square miles, three-fourths of which is in Austrian and the remainder in Prussian territory. The boundary line follows the crest of the principal chain or ridge (Riesenkamm), with the highest summits, which stretches along the northern side of the group, with an average height of over 4000 feet. Its principal peaks are the Reifträger (4430 feet), the Hohe Rad (4968 feet), the Great Sturmhaube (4862 feet), the Little Sturmhaube (4646 feet), and, near the east extremity, the Schneekoppe or Riesenkoppe (5266 feet), the loftiest mountain in northern or central Germany. Roughly parallel to this northern ridge, and separated from it by a long narrow valley known as the Siebengründe, there extends on the south a second and lower chain, of broad massive “saddles,” with comparatively few peaks. The chief heights here are the Kesselkoppe (4708 feet), the Krkonose (4849 feet), the Ziegenrücken, and the Brunnenberg (5072 feet). From both ridges spurs of greater or less length are sent off at various angles,—those from the Bohemian ridge being ...longer, broader, and less abrupt than those from the Riesenkamm. On its northern side this mountain group rises ruggedly and precipitously from the Hirschberg valley; but on its southern side its slope towards Bohemia is very much more gradual. The scenery is in general bold and wild,— the projecting crags and deep rocky gorges and precipices often presenting striking, sometimes even sublime, landscapes. The Bohemian ridge is cleft about the middle by a deep gorge through which pour the headwaters of the river Elbe, which finds its source in the Siebengründe. The Iser, Bober, Aupa, Zacken, Queiss, and a great number of smaller streams also rise among these mountains or on their skirts; and small lakes and tarns are not unfrequent in the valleys. The Great and Little Schneegruben,—two deep rocky gorge-like valleys in which snow remains all the year round—lie to the north of the Hohe Rad. Nearly the whole of the Riesenkamm and the western portion of the southern chain are granite; the eastern extremity of the main ridge and several mountains to the south-east are formed of a species of gneiss; and the greater part of the Bohemian chain, especially its summits, consists of mica-slate. Blocks of these minerals lie scattered on the sides and ridges of the mountains and in the beds of the streams; and extensive turf moors occupy many of the mountain slopes and valleys. The lower parts of the Riesengebirge are clad with forests of oak, beech, pine, and fir; above 1600 feet only the last two kinds of trees are found, and beyond about 3950 feet only the dwarf pine (Pinus Pumilio). Various alpine plants are found on the Riesengebirge,—some having been artificially introduced on the Schneekoppe. "Wheat is grown at an elevation of 1800 feet above the sea-level, and oats as high as 2700 feet. The inhabitants of this mountain region, who are tolerably numerous, especially on the Bohemian side, live for the most part, not in villages, but in scattered huts called “Bauden.” They support themselves by the rearing of cattle, tillage, glass-making, and linen-weaving. Mining is carried on only to a small extent for arsenic, although there are traces of former more extensive workings for other metals. Several spots in the Riesengebirge are a good deal frequented as summer resorts; and the Schneekoppe and other summits are annually visited by a considerable number of travellers, who find shelter in the Bauden. The Riesengebirge is the legendary home of Number Nip (Rübezahl), a half-mischievous half-friendly goblin of German folklore; and various localities in the group are more or less directly associated with his name.
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RIETI a city of Italy, in the province of Perugia, 18∣ miles south-east of Terni, which is 69 miles by rail from Rome. It occupies a fine position 1396 feet above the sea on the right bank of the Velino (a torrent sub-tributary to the Tiber), which at this point issues from the limestone plateau; the old town occupies the declivity and the new town spreads out on the level. "While with its quaint red-roofed houses, its old town walls (restored about 1250), its castle, its cathedral (13th and 15th centuries), its episcopal palace (1283, Andrea Pisano), and its various churches and convents Rieti has no small amount of mediaeval pictur-esqueness, it also displays a good deal of modern activity in wine-growing, cattle-breeding, and sugar-boiling. The fertility of the neighbourhood is celebrated both by Virgil and by Cicero. A Roman bridge over the Velino, Thorwaldsen’s monument to Isabella Alfani, and a statue of St Barbara by Berdini, both in the cathedral, and the Palazzo Vincentini by Vignola deserve to be mentioned. The population was 7875 in 1871, and 9618 (with suburbs, 13,679; in the commune, 16,822) in 1881....
According to Terentius Varro (himself perhaps of Reatino birth) and others who have followed him, the people who founded Cures, and afterwards settled on the Palatine at Rome, were natives of the Reatine territory; but this is of somewhat the same questionable character as the other story about the companion of Hercules who was buried at this point near the Via Salaria. About the Via Salaria itself, there is no doubt it led from the sea to Reate and onwards towards Ancona, and was from a very early date the great route for the conveyance of salt to the Sabine country. While hardly mentioned in connexion with the Punic or Civil Wars, Reate is described by Strabo as exhausted by those long contests. Its inhabitants received the Roman franchise at the same time with the rest of the Sabines (290 b.c.), but it appears as a praefectura and not as a municipium down to the beginning of the empire. It was never made a colonia, though veterans of the Praetorian and of the legions Octava and Décima Augusta were settled there by Vespasian, who belonged to a Reatine family and was born in the neighbourhood. For the contests of the Reatines with the people of Interamna see Terni. About the middle of the 12th century the town was besieged and captured by Roger I. of Sicily. In the struggle between church and empire it always held with the former; and it defied the forces of Frederick II. and Otho IV. Pope Nicholas IV. long resided at Rcati, and it was there he crowned Charles II. of Anjou king of the Two Sicilies. In the 14th century Robert, and afterwards Joanna, of Naples managed to keep possession of Reati for many years, but it returned to the States of the Church under Gregory IX. About the year 1500 tho liberties of the town, long defended against the encroachments of the popes, were entirely abolished. An earthquake in 1785 was in 1799 followed by the much more disastrous pillage of Reati by the papal troops for a space of fourteen days.
See Aldus Manutius, “Dissert, cpistolica de Reati,” in Not. Thes. Aηtiη. Rοrn., i.; Angelotti, Descrizione, 1G35; Sclιenardi, Antiche lapidi, 1820; and Michaeli, Note per la storia di Rieti, 1868, 1870.
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RIETSCHEL Ernst Friedrich August (1804-1861), one of the most distinguished of modern German sculptors. Born at Pulsnitz in Saxony in 1804, at an early age he became an art student at Dresden, and subsequently a pupil of Rauch in Berlin. He there gained an art studentship, and studied in Rome in 1827-28. After returning to Saxony he soon brought himself into notice by a colossal statue of Frederick Augustus, king of Saxony, was elected a member of the academy of Dresden, and thenceforth became one of the chief sculptors of his country. In 1832 he was elected to the Dresden professorship of sculpture, and had many foreign orders of merit conferred on him by the Governments of different countries. His death occurred at Dresden in 1861.
RietscheΓs style was very varied; he produced works imbued with much religious feeling, and to some extent occupied the same place as a sculptor that Overbeck did in painting. Other important works by Rietschel were purely classical in style. He was specially famed for his portrait figures of eminent men, treated with much idealism and dramatic vigour; among the latter class his chief works were colossal statues of Goethe and Schiller for the town of Weimar, of Weber for Dresden, and of Lessing for Bruns wick. He also designed the memorial statue of Luther for Worms, but died before he could carry it out. The principal among RietscheΓs religious pieces of sculpture are the well-known Christ-Angel, and a life-sized Pietà, executed for the king of Prussia. He also worked a great deal in rilievo, and produced many graceful pieces, especially a fine series of bas-reliefs representing Night and Morning, Noon aud Twilight, designed with much poetical feeling and imagination....
For a good biography of Rietschel and account of his works see Appeπnann, Ernst Rietschel, Leipsic, 18G3.
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