A History of Science - Volume 3

BY HENRY SMITH WILLIAMS, M.D., LL.D.

ASSISTED BY EDWARD H. WILLIAMS, M.D.

IN FIVE VOLUMES

VOLUME III.

Contents

DETAILED CONTENTS BOOK III. MODERN DEVELOPMENT OF THE PHYSICAL SCIENCES

CONTENTS

BOOK III

CHAPTER I. THE SUCCESSORS OF NEWTON IN ASTRONOMY

The work of Johannes Hevelius—Halley and Hevelius—Halley's observation

of the transit of Mercury, and his method of determining the parallax of

the planets—Halley's observation of meteors—His inability to

explain these bodies—The important work of James Bradley—Lacaille's

measurement of the arc of the meridian—The determination of the

question as to the exact shape of the earth—D'Alembert and his

influence upon science—Delambre's History of Astronomy—The

astronomical work of Euler.

CHAPTER II. THE PROGRESS OF MODERN ASTRONOMY

The work of William Herschel—His discovery of Uranus—His discovery

that the stars are suns—His conception of the universe—His deduction

that gravitation has caused the grouping of the heavenly bodies—The

nebula, hypothesis,—Immanuel Kant's conception of the formation of the

world—Defects in Kant's conception—Laplace's final solution of the

problem—His explanation in detail—Change in the mental attitude of the

world since Bruno—Asteroids and satellites—Discoveries of Olbersl—The

mathematical calculations of Adams and Leverrier—The discovery of the

inner ring of Saturn—Clerk Maxwell's paper on the stability of Saturn's

rings—Helmholtz's conception of the action of tidal friction—Professor

G. H. Darwin's estimate of the consequences of tidal action—Comets

and meteors—Bredichin's cometary theory—The final solution of the

structure of comets—Newcomb's estimate of the amount of cometary dust

swept up daily by the earth—The fixed stars—John Herschel's studies

of double stars—Fraunhofer's perfection of the refracting

telescope—Bessel's measurement of the parallax of a star,—Henderson's

measurements—Kirchhoff and Bunsen's perfection of the

spectroscope—Wonderful revelations of the spectroscope—Lord Kelvin's

estimate of the time that will be required for the earth to become

completely cooled—Alvan Clark's discovery of the companion star of

Sirius—The advent of the photographic film in astronomy—Dr. Huggins's

studies of nebulae—Sir Norman Lockyer's "cosmogonic guess,"—Croll's

pre-nebular theory.

CHAPTER III. THE NEW SCIENCE OF PALEONTOLOGY

William Smith and fossil shells—His discovery that fossil rocks are

arranged in regular systems—Smith's inquiries taken up by Cuvier—His

Ossements Fossiles containing the first description of hairy

elephant—His contention that fossils represent extinct species

only—Dr. Buckland's studies of English fossil-beds—Charles Lyell

combats catastrophism,—Elaboration of his ideas with reference to

the rotation of species—The establishment of the doctrine of

uniformitarianism,—Darwin's Origin of Species—Fossil man—Dr.

Falconer's visit to the fossil-beds in the valley of the

Somme—Investigations of Prestwich and Sir John Evans—Discovery of the

Neanderthal skull,—Cuvier's rejection of human fossils—The finding

of prehistoric carving on ivory—The fossil-beds of America—Professor

Marsh's paper on the fossil horses in America—The Warren mastodon,—The

Java fossil, Pithecanthropus Erectus.

CHAPTER IV. THE ORIGIN AND DEVELOPMENT OF MODERN GEOLOGY

James Hutton and the study of the rocks—His theory of the earth—His

belief in volcanic cataclysms in raising and forming the continents—His

famous paper before the Royal Society of Edinburgh, 1781—-His

conclusions that all strata of the earth have their origin at the bottom

of the sea—-His deduction that heated and expanded matter caused the

elevation of land above the sea-level—Indifference at first shown this

remarkable paper—Neptunists versus Plutonists—Scrope's classical work

on volcanoes—Final acceptance of Hutton's explanation of the origin

of granites—Lyell and uniformitarianism—Observations on the gradual

elevation of the coast-lines of Sweden and Patagonia—Observations on

the enormous amount of land erosion constantly taking place,—Agassiz

and the glacial theory—Perraudin the chamois-hunter, and his

explanation of perched bowlders—De Charpentier's acceptance of

Perraudin's explanation—Agassiz's paper on his Alpine studies—His

conclusion that the Alps were once covered with an ice-sheet—Final

acceptance of the glacial theory—The geological ages—The work of

Murchison and Sedgwick—Formation of the American continents—Past,

present, and future.

CHAPTER V. THE NEW SCIENCE OF METEOROLOGY

Biot's investigations of meteors—The observations of Brandes and

Benzenberg on the velocity of falling stars—Professor Olmstead's

observations on the meteoric shower of 1833—Confirmation of Chladni's

hypothesis of 1794—The aurora borealis—Franklin's suggestion that

it is of electrical origin—Its close association with terrestrial

magnetism—Evaporation, cloud-formation, and dew—Dalton's demonstration

that water exists in the air as an independent gas—Hutton's theory of

rain—Luke Howard's paper on clouds—Observations on dew, by Professor

Wilson and Mr. Six—Dr. Wells's essay on dew—His observations

on several appearances connected with dew—Isotherms and ocean

currents—Humboldt and the-science of comparative climatology—His

studies of ocean currents—Maury's theory that gravity is the cause

of ocean currents—Dr. Croll on Climate and Time—Cyclones and

anti-cyclones,—Dove's studies in climatology—Professor Ferrel's

mathematical law of the deflection of winds—Tyndall's estimate of

the amount of heat given off by the liberation of a pound of

vapor—Meteorological observations and weather predictions.

CHAPTER VI. MODERN THEORIES OF HEAT AND LIGHT

Josiah Wedgwood and the clay pyrometer—Count Rumford and the vibratory

theory of heat—His experiments with boring cannon to determine the

nature of heat—Causing water to boil by the friction of the borer—His

final determination that heat is a form of motion—Thomas Young and the

wave theory of light—His paper on the theory of light and colors—His

exposition of the colors of thin plates—Of the colors of thick

plates, and of striated surfaces,—Arago and Fresnel champion the wave

theory—opposition to the theory by Biot—The French Academy's tacit

acceptance of the correctness of the theory by its admission of Fresnel

as a member.

CHAPTER VII. THE MODERN DEVELOPMENT OF ELECTRICITY AND MAGNETISM

Galvani and the beginning of modern electricity—The construction of

the voltaic pile—Nicholson's and Carlisle's discovery that the galvanic

current decomposes water—Decomposition of various substances by Sir

Humphry Davy—His construction of an arc-light—The deflection of the

magnetic needle by electricity demonstrated by Oersted—Effect of

this important discovery—Ampere creates the science of

electro-dynamics—Joseph Henry's studies of electromagnets—Michael

Faraday begins his studies of electromagnetic induction—His famous

paper before the Royal Society, in 1831, in which he demonstrates

electro-magnetic induction—His explanation of Arago's

rotating disk—The search for a satisfactory method of storing

electricity—Roentgen rays, or X-rays.

CHAPTER VIII. THE CONSERVATION OF ENERGY

Faraday narrowly misses the discovery of the doctrine of

conservation—Carnot's belief that a definite quantity of work can be

transformed into a definite quantity of heat—The work of James Prescott

Joule—Investigations begun by Dr. Mayer—Mayer's paper of 1842—His

statement of the law of the conservation of energy—Mayer and

Helmholtz—Joule's paper of 1843—Joule or Mayer—Lord Kelvin and the

dissipation of energy-The final unification.

CHAPTER IX. THE ETHER AND PONDERABLE MATTER

James Clerk-Maxwell's conception of ether—Thomas Young and

"Luminiferous ether,"—Young's and Fresnel's conception of transverse

luminiferous undulations—Faraday's experiments pointing to the

existence of ether—Professor Lodge's suggestion of two ethers—Lord

Kelvin's calculation of the probable density of ether—The vortex theory

of atoms—Helmholtz's calculations in vortex motions—Professor

Tait's apparatus for creating vortex rings in the air—-The ultimate

constitution of matter as conceived by Boscovich—Davy's speculations

as to the changes that occur in the substance of matter at different

temperatures—Clausius's and Maxwell's investigations of the

kinetic theory of gases—Lord Kelvin's estimate of the size of the

molecule—Studies of the potential energy of molecules—Action of gases

at low temperatures.

APPENDIX

A HISTORY OF SCIENCE

BOOK III. MODERN DEVELOPMENT OF THE PHYSICAL SCIENCES

With the present book we enter the field of the distinctively modern. There is no precise date at which we take up each of the successive stories, but the main sweep of development has to do in each case with the nineteenth century. We shall see at once that this is a time both of rapid progress and of great differentiation. We have heard almost nothing hitherto of such sciences as paleontology, geology, and meteorology, each of which now demands full attention. Meantime, astronomy and what the workers of the elder day called natural philosophy become wonderfully diversified and present numerous phases that would have been startling enough to the star-gazers and philosophers of the earlier epoch.

Thus, for example, in the field of astronomy, Herschel is able, thanks to his perfected telescope, to discover a new planet and then to reach out into the depths of space and gain such knowledge of stars and nebulae as hitherto no one had more than dreamed of. Then, in rapid sequence, a whole coterie of hitherto unsuspected minor planets is discovered, stellar distances are measured, some members of the starry galaxy are timed in their flight, the direction of movement of the solar system itself is investigated, the spectroscope reveals the chemical composition even of suns that are unthinkably distant, and a tangible theory is grasped of the universal cycle which includes the birth and death of worlds.

Similarly the new studies of the earth's surface reveal secrets of planetary formation hitherto quite inscrutable. It becomes known that the strata of the earth's surface have been forming throughout untold ages, and that successive populations differing utterly from one another have peopled the earth in different geological epochs. The entire point of view of thoughtful men becomes changed in contemplating the history of the world in which we live—albeit the newest thought harks back to some extent to those days when the inspired thinkers of early Greece dreamed out the wonderful theories with which our earlier chapters have made our readers familiar.

In the region of natural philosophy progress is no less pronounced and no less striking. It suffices here, however, by way of anticipation, simply to name the greatest generalization of the century in physical science—the doctrine of the conservation of energy.

I. THE SUCCESSORS OF NEWTON IN ASTRONOMY

HEVELIUS AND HALLEY

STRANGELY enough, the decade immediately following Newton was one of comparative barrenness in scientific progress, the early years of the eighteenth century not being as productive of great astronomers as the later years of the seventeenth, or, for that matter, as the later years of the eighteenth century itself. Several of the prominent astronomers of the later seventeenth century lived on into the opening years of the following century, however, and the younger generation soon developed a coterie of astronomers, among whom Euler, Lagrange, Laplace, and Herschel, as we shall see, were to accomplish great things in this field before the century closed.

One of the great seventeenth-century astronomers, who died just before the close of the century, was Johannes Hevelius (1611-1687), of Dantzig, who advanced astronomy by his accurate description of the face and the spots of the moon. But he is remembered also for having retarded progress by his influence in refusing to use telescopic sights in his observations, preferring until his death the plain sights long before discarded by most other astronomers. The advantages of these telescope sights have been discussed under the article treating of Robert Hooke, but no such advantages were ever recognized by Hevelius. So great was Hevelius's reputation as an astronomer that his refusal to recognize the advantage of the telescope sights caused many astronomers to hesitate before accepting them as superior to the plain; and even the famous Halley, of whom we shall speak further in a moment, was sufficiently in doubt over the matter to pay the aged astronomer a visit to test his skill in using the old-style sights. Side by side, Hevelius and Halley made their observations, Hevelius with his old instrument and Halley with the new. The results showed slightly in the younger man's favor, but not enough to make it an entirely convincing demonstration. The explanation of this, however, did not lie in the lack of superiority of the telescopic instrument, but rather in the marvellous skill of the aged Hevelius, whose dexterity almost compensated for the defect of his instrument. What he might have accomplished could he have been induced to adopt the telescope can only be surmised.

Halley himself was by no means a tyro in matters astronomical at that time. As the only son of a wealthy soap-boiler living near London, he had been given a liberal education, and even before leaving college made such novel scientific observations as that of the change in the variation of the compass. At nineteen years of age he discovered a new method of determining the elements of the planetary orbits which was a distinct improvement over the old. The year following he sailed for the Island of St, Helena to make observations of the heavens in the southern hemisphere.

It was while in St. Helena that Halley made his famous observation of the transit of Mercury over the sun's disk, this observation being connected, indirectly at least, with his discovery of a method of determining the parallax of the planets. By parallax is meant the apparent change in the position of an object, due really to a change in the position of the observer. Thus, if we imagine two astronomers making observations of the sun from opposite sides of the earth at the same time, it is obvious that to these observers the sun will appear to be at two different points in the sky. Half the angle measuring this difference would be known as the sun's parallax. This would depend, then, upon the distance of the earth from the sun and the length of the earth's radius. Since the actual length of this radius has been determined, the parallax of any heavenly body enables the astronomer to determine its exact distance.

The parallaxes can be determined equally well, however, if two observers are separated by exactly known distances, several hundreds or thousands of miles apart. In the case of a transit of Venus across the sun's disk, for example, an observer at New York notes the image of the planet moving across the sun's disk, and notes also the exact time of this observation. In the same manner an observer at London makes similar observations. Knowing the distance between New York and London, and the different time of the passage, it is thus possible to calculate the difference of the parallaxes of the sun and a planet crossing its disk. The idea of thus determining the parallax of the planets originated, or at least was developed, by Halley, and from this phenomenon he thought it possible to conclude the dimensions of all the planetary orbits. As we shall see further on, his views were found to be correct by later astronomers.

In 1721 Halley succeeded Flamsteed as astronomer royal at the Greenwich Observatory. Although sixty-four years of age at that time his activity in astronomy continued unabated for another score of years. At Greenwich he undertook some tedious observations of the moon, and during those observations was first to detect the acceleration of mean motion. He was unable to explain this, however, and it remained for Laplace in the closing years of the century to do so, as we shall see later.

Halley's book, the Synopsis Astronomiae Cometicae, is one of the most valuable additions to astronomical literature since the time of Kepler. He was first to attempt the calculation of the orbit of a comet, having revived the ancient opinion that comets belong to the solar system, moving in eccentric orbits round the sun, and his calculation of the orbit of the comet of 1682 led him to predict correctly the return of that comet in 1758. Halley's Study of Meteors.

Like other astronomers of his time he was greatly puzzled over the well-known phenomena of shooting-stars, or meteors, making many observations himself, and examining carefully the observations of other astronomers. In 1714 he gave his views as to the origin and composition of these mysterious visitors in the earth's atmosphere. As this subject will be again referred to in a later chapter, Halley's views, representing the most advanced views of his age, are of interest.

"The theory of the air seemeth at present," he says, "to be perfectly well understood, and the differing densities thereof at all altitudes; for supposing the same air to occupy spaces reciprocally proportional to the quantity of the superior or incumbent air, I have elsewhere proved that at forty miles high the air is rarer than at the surface of the earth at three thousand times; and that the utmost height of the atmosphere, which reflects light in the Crepusculum, is not fully forty-five miles, notwithstanding which 'tis still manifest that some sort of vapors, and those in no small quantity, arise nearly to that height. An instance of this may be given in the great light the society had an account of (vide Transact. Sep., 1676) from Dr. Wallis, which was seen in very distant counties almost over all the south part of England. Of which though the doctor could not get so particular a relation as was requisite to determine the height thereof, yet from the distant places it was seen in, it could not but be very many miles high.