LIST OF ARTICLES IN THE ENCYCLOPAEDIA BRITANNICA ON ASTRONOMY
Early Ideas of the World
More than two thousand years ago the poet Lucretius, reviewing the physical knowledge and theories of the Greeks, described, as the Britannica tells us, how “the world was formed by the conjunctions of streams of atoms, which condensed into the earth, with its attendant water, air, and aether, to form a self-contained whole,” and went on to tell how in the changes of infinite time all possible forms of life appeared, but only those fittest to survive persisted. Here we have an unconscious anticipation of the nebular hypothesis and the theory of natural selection, two of the most tremendous of modern speculations. Four hundred years earlier Democritus, the greatest of the Greek natural philosophers, had said: “According to convention there is a sweet and a bitter, and according to convention there is colour. In truth there are atoms and a void.” Democritus came near announcing the doctrines of the indestructibility of matter and the conservation of energy, yet the conventions which he assailed persisted for generations: colour, taste and other qualities of a substance being regarded as of its essence and as much realities as the substance itself. The theories of the Greeks in fact held the field for centuries, until, during the Renaissance, men’s minds attacked the secrets of nature in a more modern spirit. Yet, long as has been its history, physical science, as we know it to-day, is but a few years old, the result of the feverish activity which has been the obsession of the generation now passing (Vol. 24, p. 396).
There are many entertaining touches in the historical account of the development of the physical sciences with which this section of the Britannica is enriched, for every branch of the subject has been treated from the historical point of view. The articles, too, have been written by masters who can describe clearly because they see clearly, and no reader, desiring a sound knowledge of the general principles on which science rests, and of the conclusions to which the latest investigations have directed scientific thought, will go away empty handed.
The section of the Physical Sciences in the Britannica covers, of course, an enormous field which for general purposes may be conveniently divided into:—
As a preliminary to any one of these and to the whole subject the reader will be well advised to read the articleScience(Vol. 24, p. 396), by W. C. D. Whetham of Trinity College, Cambridge, author ofRecent Development of Physical Science; those onUnits, Physical(Vol. 27, p. 738), andUnits, Dimensions of(Vol. 27, p. 736), are also of fundamental importance; and those onSpace and Time(Vol. 25, p. 525), andTime, Measurement of(Vol. 26, p. 983), may profitably be consulted.
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 ofMatter(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 underScience(Vol. 24, p. 397);Molecules(Vol. 18, p. 654);Alchemy(Vol. 1, p. 521); and modern conceptions are discussed underLiquid Gases,Cohesion(Vol. 16, p. 756); andSpectroscopy(Vol. 25, p. 625). Reference should also be made to the articlesDensity(Vol. 8, p. 46);Diffusion(Vol. 8, p. 255); and especiallyGravitation(Vol. 12, p. 384), by Professor Poynting of the University of Birmingham, andAether(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; andEnergy(Vol. 9, p. 398), andEnergetics(Vol. 9, p. 390), both by Sir Joseph Larmor. Of as great importance from the physical point of view areWave(Vol. 28, p. 424), the part of the articleMechanicsdealing with simple harmonic motion (Vol. 17, p. 975) and elliptic harmonic motion (p. 978), andHarmonic Analysis(Vol. 12, p. 956), all by Professor Lamb of the University of Manchester. Other articles which should be consulted areCapillary Action(Vol. 5, p. 256), andPerpetual Motion(Vol. 21, p. 180).
The main articleSound(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 articleHearing(Vol. 13, p. 124), the range of audibility is discussed (see alsoTartini, Vol. 26, p. 436, for an account of Tartini’s tones), while with regard to quality of tone the reader will find suggestive matter underViolin(Vol. 28, p. 104). An account of experiments in balloons on the propagation of sound, will be found (Vol. 1, p. 267) underAeronautics. Reference should also be made to the articlesWave(Vol. 28, p. 425),Elasticity,Vibrations and Waves(Vol. 9, p. 158), andHarmonic 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 articlesPhonograph(Vol. 21, p. 467),Gramophone(Vol. 12, p. 333), and especiallyStringed Instruments(Vol. 25, p. 1038),Wind Instruments(Vol. 28, p. 709), and other articles on musical instruments (see the chapter onMusicin this Guide). For accounts of the researches ofKundt(Vol. 15, p. 946),Lagrange(Vol. 16, p. 75) andStokes(Vol. 25, p. 951), see those articles.
The main articleLight(Vol. 16, p. 608) is in four parts. TheIntroductoryandHistoricalsections are by C. Everitt; that on theNatureof Light by Professor Lorentz of the University of Leiden; that on itsVelocityby 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, seePhotometry(Vol. 21, p. 525), a brilliant article by Prof. H. H. Turner, of Oxford University;Illumination(Vol. 14, p. 320).
(b)Reflection of Light(Vol. 23, p. 2);Absorption(Vol. 1, p. 76);Refraction(Vol. 23, p. 25);Dispersion(Vol. 8, p. 315);Interference(Vol. 14, p. 685);Polarization of Light(Vol. 21, p. 932).
(c)Shadow(Vol. 24, p. 738);Diffraction(Vol. 8, p. 238);Calorescence(Vol. 5, p. 60);Fluorescence(Vol. 10, p. 375);Phosphorescence(Vol. 21, p. 476).
(d)Mirror(Vol. 18, p. 575);Lens(Vol. 16, p. 421);Caustic(Vol. 5, p. 558);Aberration(Vol. 1, p. 54).
(e)Corona(Vol. 7, p. 184);Halo(Vol. 12, p. 864);Mirage(Vol. 18, p. 573);Rainbow(Vol. 22, p. 861);Sky(Vol. 25, p. 202);Twilight(Vol. 26, p. 492)—see alsoDust(Vol. 8, p. 713).
(f)Telescope(Vol. 26, p. 557);Microscope(Vol. 18, p. 392);Objective(Vol. 19, p. 948);Camera Lucida(Vol. 5, p. 104);Camera Obscura(Vol. 5, p. 104);Binocular Instrument(Vol. 3, p. 949);Stereoscope(Vol. 25, p. 895).
(g)Vision(Vol. 28, p. 130).
Far reaching developments are described inPhotography(Vol. 21, p. 485) andSpectroscopy(Vol. 25, p. 619). In the former article Sir W. de W. Abney describes in great detail photographicProcesses; Major-General Waterhouse,ApparatusandLenses, while A. H. Hinton discusses thePictorialaspect of the subject. There are also valuable articles onCelestial Photography(Vol. 21, p. 523), by Professor Turner, and on theSpectroHeliograph(Vol. 25, p. 618), by the inventor, G. E. Hale, director of the Solar Observatory of the Carnegie Institution at Mount Wilson, Cal. The relation between magnetism and light is discussed in an articleMagneto-Optics(Vol. 17, p. 388), by Sir J. J. Thomson.
The treatment of this subject in the Encyclopaedia Britannica has been generally organized by Prof. H. L. Callendar, of the Royal College of Science, London, who was designated by Lord Kelvin as his successor in this department of the work. In pursuing the subject the following order may conveniently be followed:
(a)Heat(Vol. 13, p. 135),Thermometry(Vol. 26, p. 821),Calorimetry(Vol. 5, p. 60), andThermodynamics(Vol. 26, p. 808), all by Professor Callendar;Cold(Vol. 6, p. 663).
(b)Conduction of Heat(Vol. 6, p. 890);Radiation, Theory of(Vol. 22, p. 785);Radiometer(Vol. 22, p. 806).
(c)Fusion(Vol. 11, p. 369);Vaporization(Vol. 27, p. 897);Condensation of Gases(Vol. 6, p. 844);Liquid Gases(Vol. 16, p. 744);Thermoelectricity(Vol. 26, p. 814).
Historical
We are so accustomed to think of electricity as the peculiar possession of our own age (the first crude attempts at an electric light were only two score years ago)that we are apt to forget that the first experiments in the science were made at least 2500 years ago. The first effort to place it on a true experimental and inductive basis dates back more than three centuries to the publication of the researches ofWilliam Gilbert(see Vol. 12, p. 9), the most distinguished man of science of his time, whom Queen Elizabeth appointed her private physician at the “usual” salary of £100. A hundred years later,Volta(Vol. 28, p. 198), who might be called the patron saint of electricity, produced the first electric current with the pile which bears his name. MeanwhileBenjamin Franklin(Vol. 11, p. 30) had been experimenting with his famous kite, andCavendish(Vol. 5, p. 580) andCoulomb(Vol. 7, p. 508) had been paving the way for the startling developments which resulted from Volta’s invention. In the 19th centuryFaraday(Vol. 10, p. 173),Ampère(Vol. 1, p. 878),Ohm(Vol. 20, p. 34),Lord Kelvin(Vol. 15, p. 721),James Clerk Maxwell(Vol. 17, p. 929) and other brilliant investigators in rapid succession developed the field, until the science and application of electricity have attained a position absolutely dominating our daily life.
Analysis of the Subject
The section of the Britannica treating this great subject is therefore one of the most important in the whole work, and it was in the fullest recognition of the fact that the editor asked Prof. J. A. Fleming, of the University of London, famous for his original work in both the mathematical and the experimental branches of the science, to organize the sections for the new edition. The ground is generally covered in the four articles, on electricity, electrostatics, electrokinetics, and electromagnetism, all contributed by Prof. Fleming himself. The articleElectricity(Vol. 9, p. 179) is the key article to the subject, and should be read first. The two great branches of electrical theory then follow: (a)Electrostatics(Vol. 9, p. 240), in connection with which the articleElectrical Machine(Vol. 9, p. 176) should also be studied, with reference toElectroscope(Vol. 9, p. 239) andElectrophorus(Vol. 9, p. 237). (b)Electrokinetics(Vol. 9, p. 210) and, supplementing it,Conduction, Electric(Vol. 6, p. 855). The latter is divided into three parts: (i.)Conduction in Solids, by Prof. Fleming; (ii.)Conduction in Liquidsby W. C. D. Whetham; (iii.)Conduction in Gases, by Sir J. J. Thomson. In connection with (ii.) should be readElectrolysis(Vol. 9, p. 217), by W. C. D. Whetham, and with (iii.)Röntgen Rays(Vol. 23, p. 694) andVacuum Tube(Vol. 27, p. 834), both by Sir J. J. Thomson, whose articleElectric Waves(Vol. 9, p. 203) is of fundamental importance. The general principles of electrical engineering are set out in the articleElectric Supply(Vol. 9, p. 193) with reference toDynamo(Vol. 8, p. 764);Motors, Electric(Vol. 18, p. 910);Transformers(Vol. 27, p. 173);Accumulator(Vol. 1, p. 126);Power Transmission,Electric(Vol. 22, p. 233);Traction,Electric Traction(Vol. 27, p. 120);Lighting,Electric(Vol. 16, p. 659); see alsoElectrochemistry(Vol. 9, p. 208) andElectrometallurgy(Vol. 9, p. 232);Telegraph(Vol. 26, p. 510);Telephone(Vol. 26, p. 547).
A bridge toMagnetism(Vol. 17, p. 321), an article by Shelford Bidwell, former president of the Physical Society, is the articleElectromagnetism(Vol. 9, p. 226), by Prof. Fleming. This article leads also to the study of manifestations in nature of electricity and magnetism: see the articlesAtmospheric Electricity(Vol. 2, p. 860);Aurora Polaris(Vol. 2, p. 927);Earth Currents(Vol. 8, p. 813); andMagnetism, Terrestrial(Vol. 17, p. 353); and to the applications of its principlesin theCompass(Vol. 6, p. 804).
An alphabetical list of the articles in the Britannica on the subjects treated in this chapter is given below. The biographies of distinguished physicists, included in the list, are valuable as containing accounts of their contributions to science, and are full of human interest.
We have traveled far since Chemistry had as its simple basis four elements: fire, air, water, and earth, regarded as perfect and complete since they embody every essence of which a body was supposedly capable: for fire was hot and dry; air, hot and wet; water, cold and wet; earth, cold and dry. We have outlived the belief in the philosopher’s stone which animated the Middle Ages. Yet these fallacies are but manifestations of the effort—old as thought—to reduce the manifoldness of matter to primordial elements, from which, in one form or other, every substance should be capable of being built up. The ultimate problem of chemistry is, therefore, the constitution of matter, and the fight around this is waged on the marches of the physical and chemical sciences.
Triumphs of Chemistry
The great commercial triumphs of chemistry are, of course, those due to the conquest of waste, to the utilization of by-products which for thousands of years had been regarded as useless. We are all familiar with the uses to which the by-products of coal-tar are put; we swallow one derivative to relieve headache, we may sugar our tea and flavour our ice-cream with others; with one derivative we clean our clothes which have been dyed with others; and we disinfect them with yet another. Phenacetin, saccharin, synthetic vanilla, benzine, naphthaline, analine dyes, carbolic acid, are only a few of the many substances won to the consumer by the chemist in his laboratory; and this is only one field of research. The chemist is always busy (as now with rubber, camphor, etc.), working at the synthesis of natural products in the hope that he will be able tofind a means of manufacturing them in quantities at a cost which will make them, commercially possible, and thus lessen the drain on the world’s natural supply. In almost every detail of our lives this science enters so familiarly that we forget that the many things made possible by the chemist do not simply “happen,” but are the result of laborious research in the laboratory.
It is not possible to attain proficiency in any experimental science without laboratory work; but to the student of chemistry the lucid and original articles in the Britannica will provide a most useful commentary on his work with test-tube and burner. The general reader will find in these articles an admirable survey of the subject, and of its bearings on problems of daily life. The main articleChemistry(Vol. 6, p. 33) generally covers the ground, and serves as an introduction to separate articles on important divisions of the subject. Following its arrangement the scheme outlined below suggests a useful course of reading.
(i.) Chemistry,History(Vol. 6, p. 33). Supplementary to this section are the articlesAlchemy(Vol. 1, p. 519),Element(Vol. 9, p. 253),Molecule(Vol. 18, p. 654),Atom(Vol. 2, p. 870); and reference may also be made toMedicine,Iatro-chemical School(Vol. 18, p. 50).
(ii.) Chemistry,General Principles(Vol. 6, p. 39), with reference toValency(Vol. 27, p. 847),Chemical Action(Vol. 6, p. 26),Catalysis(Vol. 5, p. 501),Isomerism(Vol. 14, p. 881),Stereo-isomerism(Vol. 25, p. 890),Radioactivity(Vol. 22, p. 793).
(iii.)Inorganic Chemistry(Vol. 6, p. 44). See alsoAcid(Vol. 1, p. 145),Alkali(Vol. 1, p. 674), and the list of 138 elements and compounds under this heading below.
(iv.)Organic Chemistry(Vol. 6, p. 47), with all the 240 articles enumerated under this heading below, especially that onPolymethylenes(Vol. 22, p. 29); see alsoExplosives(Vol. 10, p. 81).
(v.)Analytical Chemistry(Vol. 6, p. 60), with which may be consulted,Blow Pipe(Vol. 4, p. 89),Distillation(Vol. 8, p. 318),Electrolysis(Vol. 9, p. 217),Indicator(Vol. 14, p. 482),Solution(Vol. 25, p. 368),Stoichiometry(Vol. 25, p. 939).
(vi.)Physical Chemistry(Vol. 6, p. 65) supplemented byEnergetics(Vol. 9, p. 390),Chemical Action(Vol. 6, p. 26),Thermochemistry(Vol. 26, p. 804),Solution(Vol. 25, p. 368),Distillation(Vol. 8, p. 318),Condensation of Gases(Vol. 6, p. 844), with the important articlesPhotochemistry(Vol. 21, p. 484),Electrochemistry(Vol. 9, p. 208),Metallurgy(Vol. 18, p. 203),Electrometallurgy(Vol. 9, p. 232),Assaying(Vol. 2, p. 776).
Among the contributors to the chemical department of the Britannica are: Professor Ernest Rutherford, of the University of Manchester; Walter Nernst, professor of physical chemistry in the University of Berlin; W. C. D. Whetham, author ofTheory of Solution, etc.; Prof. James Walker of the University of Edinburgh; Johannes Diderik van der Waals, professor of physics, University of Amsterdam; W. R. E. Hodgkinson, professor of chemistry and physics, Ordnance College, Woolwich, perhaps the greatest living authority on explosives.
The following is a classified list of the articles on Chemistry which are contained in the Britannica. For discussions of the application of chemistry to photography, the reader should consult the articlePhotography(Vol. 21, p. 485), of which the chemical section is by Sir W. de W. Abney, adviser in Science to the English Board of Education.
CHEMISTRY—GENERAL