(I) Matter and Motion
Matter
Since all physical phenomena are manifestations, in one form or other, of matter in motion, this first division of the subject is introductory to all the rest, and should preferably be studied first. The latest theories in connection with the properties of Matter (Vol. 17, p. 891) are discussed by Sir J. J. Thomson, professor of experimental physics, Cambridge University, who has led the way in the investigation of the electrical theory of matter. The article is directed to the establishment of the electronic theory, and in view of the vast amount of original work which the author has carried out in this field, his treatment in the Britannica should be welcome to all students of physical science. Supplementing this are the following: Element, by Wilhelm Ostwald (Nobel Prizeman in Chemistry, 1909), especially the concluding remarks (Vol. 9, p. 253); Atom (Vol. 2, p. 870); Electricity, Electronic Theory (Vol. 9, p. 192). Early hypotheses are described under Science (Vol. 24, p. 397); Molecules (Vol. 18, p. 654); Alchemy (Vol. 1, p. 521); and modern conceptions are discussed under Liquid Gases, Cohesion (Vol. 16, p. 756); and Spectroscopy (Vol. 25, p. 625). Reference should also be made to the articles Density (Vol. 8, p. 46); Diffusion (Vol. 8, p. 255); and especially Gravitation (Vol. 12, p. 384), by Professor Poynting of the University of Birmingham, and Aether (Vol. 1, p. 292), by Sir Joseph Larmor, secretary of the Royal Society.
Motion
The principal articles dealing with motion are: Motion, Laws of (Vol. 18, p. 906), which deals mainly with Newton’s Laws; and Energy (Vol. 9, p. 398), and Energetics (Vol. 9, p. 390), both by Sir Joseph Larmor. Of as great importance from the physical point of view are Wave (Vol. 28, p. 424), the part of the article Mechanics dealing with simple harmonic motion (Vol. 17, p. 975) and elliptic harmonic motion (p. 978), and Harmonic Analysis (Vol. 12, p. 956), all by Professor Lamb of the University of Manchester. Other articles which should be consulted are Capillary Action (Vol. 5, p. 256), and Perpetual Motion (Vol. 21, p. 180).
(II) Sound
The main article Sound (Vol. 25, p. 437) is by Prof. J. H. Poynting of the University of Birmingham, and very completely covers the subject; the reader will, however, wish to refer to several other articles for supplementary information. Thus in the article Hearing (Vol. 13, p. 124), the range of audibility is discussed (see also Tartini, Vol. 26, p. 436, for an account of Tartini’s tones), while with regard to quality of tone the reader will find suggestive matter under Violin (Vol. 28, p. 104). An account of experiments in balloons on the propagation of sound, will be found (Vol. 1, p. 267) under Aeronautics. Reference should also be made to the articles Wave (Vol. 28, p. 425), Elasticity, Vibrations and Waves (Vol. 9, p. 158), and Harmonic Analysis (Vol. 12, p. 956) for a discussion of the form of sound waves. For applications of the principles of sound production, see also the articles Phonograph (Vol. 21, p. 467), Gramophone (Vol. 12, p. 333), and especially Stringed Instruments (Vol. 25, p. 1038), Wind Instruments (Vol. 28, p. 709), and other articles on musical instruments (see the chapter on Music in this Guide). For accounts of the researches of Kundt (Vol. 15, p. 946), Lagrange (Vol. 16, p. 75) and Stokes (Vol. 25, p. 951), see those articles.
(III) Light
The main article Light (Vol. 16, p. 608) is in four parts. The Introductory and Historical sections are by C. Everitt; that on the Nature of Light by Professor Lorentz of the University of Leiden; that on its Velocity by the late Simon Newcomb, the eminent American astronomer. The different phenomena connected with the subject may conveniently be grouped and studied as follows:—
(a) Colour (Vol. 6, p. 728); Intensity, see Photometry (Vol. 21, p. 525), a brilliant article by Prof. H. H. Turner, of Oxford University; Illumination (Vol. 14, p. 320).