D I A 731 



According to Aristoxenus, in this genus the tetra- 

 chord was divided into 30 equal parts, and was thus 

 composed, viz. 6+12 + 12=30, or, 



*|ths or f X 4th=101.5984282 + 2 f + 9 m 

 j^ths or fx4th= 101. 5984272 + 2 f + 9 m 

 ^ths or f X 4th= 50.8031452 + f + 4 m 



© I D 



4th=254.0000002+5f+ 22 m 



is, 



According to Archytas, Dr Wallis, &c. it was thus di- 

 vided, viz. ttX|Xt=I' wl " ch in our notation 

 I— 1 1 7.947096 2 + 2f + 1 Om 

 §-= 104.0000002 + 2f+ 9m 

 4^=32.0529042+ f+ 3m 



4th.=254.000000 2 + 5f + 22m 



DIATONICUM Mollb, or soft diatonic. This ge- 

 nus, according to Euclid, ascended by a hemitone or 

 half major tone, an incomposite or spiss interval, and a 

 trihemitone, composed of five quadrantal dieses or quar- 

 ters of a major tone, making up the tetrachord, which, 

 in our notation, will stand thus, viz. 



*T=129.9271352 + 3f+llm 



72.0767962+ f+ 6m 



£T= 51.9960692 + f+ 5m 



4th= 254.0000002 +5f+22m 

 The incomposite of this system was, it is said, by Dr 

 Holder, accounted to be three quadrantal dieses, or f T 

 = 78.072865 2 + f + 7m, but which exceeds it by 

 5.9960692 + m, being |ct, or the schisma of Galileo and 

 Glareanus, which differences, as in the genus Chroma- 

 ticum Molle, &c. (which see) is occasioned by the an- 

 cients having assumed, that two and a half major tones 

 were equal to a fourth instead of 2^T=4th + |d, as 

 the fact is. 



According to Aristoxenus, the tetrachord was here 

 divided into SO equal parts, of which the same was com- 

 posed as follows, viz. 6 + 9+15=30, or, 



Lths or i X 4th= 1 26.925 1 6952 + 3f + 1 lm 

 JLx 4th.- 76.27168552+ f+ 7 m 

 f X*th= 50.80314502+ f+ 4m 



3 °\ 

 •3%-ths or 



T%ths or 



4th= 254.00000002 +5f+ 22m 

 According to Ptolemy, it was, however, constituted 

 thus, viz. SX^XJ4 or 



■J =117.9*7096 2 +2f+ 10m 

 ,%= 93.0000002 +2f+ 8m 

 £§=: 43.0529042+ f+ 4m 



4th=254.0C00002 +5f+22m 



And Dr Pepuseh and Mr Overend are of opinion that 

 this genus was as follows, viz, 



T + E=1252+2f+llin 



2d = 722+2f+ 6m 



S= 572+ f+ 5m 



4th=2542+5f+22m 

 DIATONICUM Tonicum, was a genus of Ptolemy, 

 which, according to Dr Wallis, was thus constituted, viz. 

 5 jX^Xf=|> which, in our notation, is as follows, 

 £ = 104.0000002 +2f+ 9m 

 I = 1 17-9470962 +2f+10m 

 ^■zz 32.0529042+ f+ 3m 



4th= 254.000000 2 +5f+22m 



This differs from one of the preceding genera, only by 

 the arrangement of the intervals. 



DIATONUM, in Music, according to Mr Henfling, 

 is an interval whose ratio is 4-f, = 57 2 + f + 5 m, or 

 the Semitone Major, which see. 



DIAZEUTIC Tone, in Music, an interval whose 

 ratio is 4, =104 2 + 2 f + 9 m, or the Tone Major. 

 See that article. ($) 



DICEROS, a genus of plants of the class Didyna- 

 mia, and order Angiospermia. See Botany, p 258. 



DlCHONDRA, a genus of plants of the class Pen- 

 tandria, and order Digynia. See Brown's Prodrom. 

 Plant Nov. HolL Sfc. p. 490; and Botany, p. 160 and 

 179- 



DICHROMA, a genus of plants of the class Trian- 

 dria, and order Monogynia. See Botany, p. 112. 



DICKSONIA. See Filices. 



DICOTYLEDONES. See Botany, p. 78. 



DICRANUM. See Musci. 



DICTAMMUS, a genus of plants of the class De- 

 candria, and order Monogynia. See Botany, p. 210. 



DICTATOR. See Rome. 



DIDELTA, a genus of plants of the class Syngene- 

 sia, and order Polygamia Trustanea. See Botany, p. 

 307. 



DIDEROT, Denys, a French author of considerable 

 celebrity, was the son of a master-cutler at Lan- 

 gres, where he was born in the year 1713. He derived 

 his elementary instruction from the Jesuits, who, find- 

 ing him to be a youth of promising talents, were desi- 

 rous of retaining him in their society ; but he evinced 

 no inclination for the ecclesiastical life, and his father, 

 therefore, sent him to Paris to finish his studies, intend- 

 ing that he should follow the profession of the law. Di- 

 derot, however, exhibited an early partiality for litera- 

 ry pursuits, to which he addicted himself in a degree 

 that was incompatible with the duties of his situation. 

 His father having taken offence at his conduct, refused, 

 for some time, to continue his support. But young 

 Diderot, undismayed by difficulties, continued to pro- 

 secute his studies in physics, geometry, and metaphy- 

 sics, in which, and in the belles leltres, he made consi- 

 derable progress. He commenced his career as an 

 author about the age of thirty ; and one of the earliest 

 of his publications was a translation of Stanyan's Histo- 

 ry of Greece from the English. In 1745, he published 

 a small work, entitled Principles of Moral Philosophy ; 

 and in the following spring appeared his Pcnsees Philo- 

 sophiques, which procured him considerable reputation. 

 From this period he was regarded as a disciple of the 

 new philosophy, of which he afterwards became one of 

 the most able and indefatigable advocates. He repub- 

 lished his Pensies under the title of Etrennes avx es- 

 prits forts, when they obtained a very general circula- 

 tion, and contributed greatly to the dissemination of 

 those philosophical opinions which were for a long time 

 so prevalent in France. 



About this period, Diderot, in concert with D' Alem- 

 bert, laid the foundation of the famous Dictionnaire En- 

 cyclopedique ; a work which formed a sort of epoch in 

 the annals of science, and which appears to have been 

 intended to serve, not only as a magazine of all hu- 

 man knowledge, but as an engine to subvert all esta- 

 blished opinions. The first edition of this work was 

 published between the years 1751 and 1767, in 28 vo- 

 lumes, folio. The reader may be desirous of knowing 

 something of the history of the conduct and progress of 

 an undertaking, which had so great an influence on the 

 current of public opinion ; and the Memoires of Baron 



Diatonum 



II 

 Diderot. 



