INDEX. 



775 



Decyphering, 124. 



Deduction, 11, 49. 



Deductive reasoning, 534; miscel- 

 laneous forms of, 60 : probable, 

 209. 



Definition, 39, 62, 711, 723 ; pur- 

 pose of, 54 ; of cause and power, 

 224. 



De Morgan, Augustus, negative 

 terms, 14 ; Aristotle's logic, 18 ; 

 relatives, 23 ; logical universe, 

 43 ; complex propositions, 75 ; 

 contraposition, 83 ; formal logic 

 quoted, 101 ; error of his system, 

 117 ; anagram of his name, 128 ; 

 numerically definite reasoning, 

 168-172 ; probability, 198 ; belief, 

 199 ; experiments in probability, 

 207 ; probable deductive argu- 

 ments, 209-210 ; trisection of 

 angle, 233 ; probability of infer- 

 ence. 259 ; arcual unit, 306 ; 

 mathematical tables, 331 ; per- 

 sonal error, 348 ; average, 363 ; 

 his works on probability, 394- 

 395 ; apparent sequence, 409 : 

 sub.equality, 480 ; rule of ap- 

 proximation, 481 ; negative areas, 

 529 ; generalisation, 600 ; double 

 algebra, 634 ; bibliography, 716 ; 

 catalogues, 716 ; extensions of 

 algebra, 758. 



Density, unit of, 316 ; of earth, 

 387 ; negative, 642. 



Descartes, vortices, 517 : geometry, 

 632. 



Description, 62. 



Design, 762-763. 



Determinants, inference by, 50. 



Development, logical, 89, 97. 



Diagnosis, 708. 



Dichotomy, 703. 



Difference, 44 ; law of, 5 ; sign of, 

 17 ; representation of, 45 ; infer- 

 ence with, 52, 166 ; form of, 158. 



Differences of numbers, 185. 



Differential calculus, 477. 



Differential thermometer, 345. 



Diffraction of light, 420. 



Dimensions, theory of, 325. 



Dip-needle, observation of, 355. 



Direct deduction, 49. 



Direction of motion, 47. 



Discontinuity, 620. 



Discordance, of theory and experi- 

 ment, 558 ; of theories, 587. 



Discoveries, accidental, 529; pre- 

 dieted, 536 ; scope for, 752. 



Discrimination, 24 ; power of, 4. 



Disjunctive, terms, 66; conjunction, 

 67 ; propositions, 66 ; syllogism, 

 77 ; argument, 106. 



Dissipation of energy, 310. 



Distance of statements, 144. 



Divergence from average. 188. 



Diversity, 156. 



Divine interference, 765. 



Dollond, achromatic lenses, 608. 



Donkin, Professor, 375 ; on proba- 

 bility, 199, 216; principle of 

 inverse method, 244. 



Double refraction, 426. 



Dove's law of winds, 534. 



Draper's law, 606. . . 



Drobitsch, 15. 



Duality, 73, 81 ; law of, 5, 45, 92, 

 97. 



Dulong and Petit, 341, 471. 



Duration, 308. 



e, 330, 769. 



Earth, density of, 387 ; ellipticity, 



565. 

 Eclipses, 656 ; Egyptian records of, 



246 ; of Jupiter's satellites, 294, 



372 ; solar, 486. 

 Electric, sense, 405; acid, 428; 



fluid, 523. 

 Electric telegraph, anticipations of, 



671. 

 Electricity, theories of, 522 ; duality 



of, 590. 



Electrolysis, 428, 530. 

 Electro-magnet, use of, 423. 

 Elements, confusion of, 237 ; defini- 

 tion, 427 ; classification, 676, 



677, 690. ' 

 Elimination, 58. 



Ellicott, observation on clocks, 455. 

 Ellipsis, 41 ; of terms, 67. 

 Elliptic variation, 474. 

 Ellipticity of earth, 565. 

 Ellis, A. J. , contributions to formal 



logic, 172. 



Elite, Leslie, 23, 375. 

 Ellis, W., on moon's influence, 410. 

 Emanation, law of, 463. 

 Emotions, 732. 

 Empirical, knowledge, 505, 525- 



526 ; measurement, 552. 

 Encke, on mean, 386, 389 ; his 



comet, 570, 605 ; en resisting 



