have been recovered. Diophantus has sometimes been spoken of as the father of algebraical analysis, but the probability is that he borrowed it from the East. The Diophantine analysis or problems are certain questions relating to the squares and higher powers of numbers, the properties of which were first discussed in his arithmetic. The symbols used by him are different from those which have been handed down to us from other sources. The sign of subtraction resembles plus more than minus, and he denotes the square of a number by the contraction of the Greek word for power. Hypatia of Alexandria wrote a commentary on the "Arithmetic" in the fifth century, but the work was lost to the world till it was discovered by Regiomontanus in the libraries of Italy. The earliest printed edition is that of Xylander, who followed the manuscript in the university of Wittenberg, and added the book on polygonal numbers, usually but erroneously ascribed to Diophantus. Peter Fermat, son of the great mathematician of that name, published an edition, with the valuable notes his father had written on the margin of a copy of a former edition. It was in these notes that Fermat first indicated his beautiful researches on the theory of numbers. According to an epitaph, given in the form of a problem, and preserved in the Greek Anthology, a sixth part of his life belonged to the period of childhood, and a twelfth to that of youth. After this he spent a seventh part of his life in the married state, without a child, but five years subsequently he had a son, who died after having attained half the age of his father; the latter surviving the former by five years. The solution of the problem gives forty-four as the age at which he died.—W. L. M.
DIOSCORIDES, Pedacius or Pedanius, was the author of a treatise on materia medica. Very little is known of his life. It is commonly believed that he belonged to Anazarba in Cilicia Campestris; and that he was a physician by profession. Whether he lived in the first or second century is uncertain. From the fact of Pliny's not mentioning him, it is supposed that he was somewhat later. He is the author of Περι Υλης Ιατρικης in five books, which, judged by the standard and knowledge of the time it appeared in, is a work remarkable for ability, research, knowledge, and erudition. It contains a description of all articles used as medicine, and their virtues. For a long time after it was appealed to as an authority, without much addition being made to it. The part which relates to the plants of Greece has been illustrated in the great work begun by Sibthorp, and since completed by Lindley in ten volumes. In addition to the work on materia medica, Dioscorides is said to have published, on poisons; on poisoned animals; on medicines easily procurable, both simple and compound, &c. An edition of the whole was published by J. A. Saracenus, in Greek and Latin, Frankf., 1598, folio. G. Sprengel has also edited them at Leipzig, 1829-30, 2 vols. 8vo, in two languages. An Arabic translation of the treatise on materia medica is found in MS. in various European libraries.—S. D.
DIOSCORIDES or DIOSCURIDES of Ægea, one of the four great gem engravers of antiquity recorded by Pliny. The other three are Pyrgoteles, Apollonides, and Cronius. Whilst the works of these, as they come down to us, are very few, and often of a doubtful authorship, those of Dioscorides, as well for number as for merit and authenticity, are among the most important relics of antiquity. According to Pliny, the chief claim to celebrity of this renowned artist consists in his having engraved the portrait of Augustus on a stone which was used as a seal, not only by that emperor, but by a number of his successors. The relics of the genius of Dioscorides are to be found scattered among the great European collections. He flourished about the time of Augustus and Tiberius.—R. M.
DIOSCORUS, was set up as an anti-pope upon the election of Boniface II. to succeed Felix III., in the year 530. The occasion of the schism is uncertain, but it was put an end to within a few days by the death of Dioscorus.—T. A.
DIOTISALVI, the Italian architect who designed and erected the baptistery of Pisa; one of the earliest champions of the great Tuscan Rinascimento. He is believed to have been a native of Pisa. The date of the beginning of the stupendous building which has immortalized his name is put down at 1152; this date, as well as the name of the architect, being recorded in an inscription existing in the building itself. His work presents an interesting amalgamation of the ancient or Greco-Roman style, with a great deal which is evidently Lombard or Gothic. Of the life of this architect little is known, and little can be said; of his work much could be said, were this the proper place for it. Quatremere de Quincy, in his lives of celebrated architects, when, comparing this building with the similar one at Florence, built six centuries later, concludes by stating—"The baptistery of Florence is a reminiscence of a lost taste; that of Pisa is the precursor of the good style of architecture, just at its dawn."—R. M.
DIPŒNUS and SCILLIS, the first Greek sculptors who are said to have used marble in their works, were natives of Crete, and lived about 580 b.c.—R. M.
DIPPEL, Johann Conrad, an eccentric German physician who gave himself the name of Christianus Democritus, was born at the castle of Frankenstein, where his father was a Lutheran minister. He studied theology at the university of Giessen, and early in life published two works, the one entitled "Orthodoxia Orthodoxorum," and the other "Axioma veteris Adami detectum et discussum." After this he gave a course of physico-chiromantic lectures at Strasburg, where he led so irregular a life that he was at last forced to quit the city. He then returned to Germany and published his "Papismus Vapulans." This work, in which he attacks the protestants, raised him up many enemies. Dippel now turned his attention to medicine and alchemy, but his irregular habits had plunged him in debt, and a considerable number of his remaining years were spent in travelling from town to town in order to elude the vigilance of his creditors. During this period of anxious vagabondage, he made the acquaintance of the prisons of Berlin, Copenhagen, Frankfort, Leyden, Amsterdam, Altona, and Hamburg. A false report of his death having several times got abroad, he gave the world in 1733 a kind of certificated promise that he would not die till 1808; but the grim king seemed to be in haste to prove the alchemist a false prophet. On the 25th of April of the following year poor Dippel was found lifeless in his bed at the castle of Witgenstein. Dippel invented Prussian blue, and an empyreumatic oil, still called by his name, which he offered as a sort of panacea.—R. M., A.
* DIRICHLET, Peter Gustaf, a celebrated German mathematician, was born at Düren in the Rhine provinces, on the 11th February, 1805. He came early to France, and at the house of General Foy made the acquaintance of several eminent mathematicians. When only twenty years of age he gained a considerable reputation by his dissertation entitled "On the impossibility of some indeterminate equations of the fifth degree." After this he returned to his native country, and graduated at the university of Breslau in 1827. In the following year he became ordinary professor of the mathematical sciences at Berlin, and has filled since 1855 the chair of mathematics in the university of Göttingen. The French Institute, of which he had been a corresponding member since 1833, elected him in 1854 foreign associate on the death of Leopold von Buch. Dirichlet has won for himself the reputation of one of the first geometricians of the time. Many of his papers are to be found in the Dissertations of the Academy of Sciences of Berlin, and in Crelle's Journal of Pure and Applied Mathematics.—R. M., A.
DISNEY, a learned English divine and magistrate, was born at Lincoln in 1677, and died on February 3, 1720. He was educated at a private academy belonging to the protestant dissenters, and, being designed for the profession of law, was for some time a member of the middle temple. He never practised at the bar, but became one of the best magistrates of his time. He was diligent, disinterested, and impartial, and received on more than one occasion the thanks of the judges of the circuit for services rendered to his country. He was particularly active in the suppression of vice and immorality, and acted in concert with those societies which were established during the reign of Queen Anne for promoting reformation of manners. After twenty years' active duty on the bench, Disney conceived the design of becoming a minister in the Church of England, with which he had communicated from the time he had attained to manhood. His desire for holy orders was warmly applauded by Dr. Wake, archbishop of Canterbury, and he was accordingly ordained deacon, and afterwards priest in 1719. He was presented in the same year to the vicarage of Croft and to the rectory of Kirkby-super-Baine, and in the following year was instituted to the vicarage of St. Mary in Nottingham, where he remained till his death. Disney had been at much pains in collecting materials for an extensive work to be entitled "Corpus Legum de Moribus Reformandis," but his comparatively early death prevented its
