Triumphs and Wonders of the 19th Century: The True Mirror of a Phenomenal Era / A volume of original, entertaining and instructive historic and descriptive writings, showing the many and marvellous achievements which distinguish an hundred years of material, intellectual, social and moral progress

Astronomy, the oldest of all the family of sciences, is not a whit behind its sister branches in activity of research and brilliance of discovery. The assiduity and zeal of its devotees are marvelous. The celestial field is so wide, the depths of space between the stars so vast, that no assurance can ever be given to an astronomer that a lifetime of faithful and intelligent research will be rewarded with even a single discovery of importance. In this respect it differs materially from other branches of science.

Nevertheless the patient labor of those who serve in its temple has rarely failed to receive an adequate reward. The discovery made in August, 1877, by Professor Asaph Hall, of Washington, that the planet Mars is attended by two satellites, is a convincing illustration of this peculiarity of the pursuit of astronomy as a study. An indefatigable watcher of the skies for many years, Professor Hall, looking at this planet at its opposition in 1877, when it was unusually near to the earth, was surprised to note two tiny points of light quite close to it; seeing them again the next evening, changed in their positions relative to Mars, it flashed upon him that the firm tradition that Mars had no moons was now disproved. His name will be forever associated with these two bodies, Deimos and Phobos, as their discoverer, although they are but wee orbs, only seven miles in diameter.

I. ASTRONOMY A CENTURY AGO.

The end of the eighteenth century found the Copernican theory of astronomy well established, the principles laid down by Kepler and Newton fully elaborated, and the application of the higher mathematics to the needs of astronomy complete. But there were, as yet, no large telescopes, and observatories were few. In Germany, a great disposition to make observations in this science and in meteorology was displayed in 1783 and for a few years following, and the records then made have proved of much value in confirming discoveries announced at later periods.

When Sir William Herschel, on March 13, 1781, pointed out a little star in the constellation of the Twins, and found that it had a perceptible disk and a slight motion, and was therefore not a star, but a newly found planet, to which the name Uranus was soon given, a careful inspection of the notebooks of previous observers showed that Uranus had been observed and recorded as a fixed star on twenty previous occasions in that century. One man had seen it twelve times, and made his record of it on a paper bag purchased at a perfumer’s. Had he been a man of sufficient order and method to have penned what he saw on the regular records of his observatory, to him would have come the glory of the great discovery of that century.

II. HOW “BODE’S LAW” PROMOTED RESEARCH.

An erroneous guess, if it is a good guess, sometimes produces excellent results. In 1778, Bode, of Berlin, published a “law” that states the distances of the various planets from the sun. It is often expressed simply in this way: Set down 4, and add to it successively the numbers 3, 6, 12, 24, etc., and the sums obtained, viz., 4, 7, 10, 16, 28, etc., represent the relative distances of all the planets from the sun, viz., Mercury 4, Venus 7, Earth 10, Mars 16, [Asteroids 28], Jupiter 52, etc. In reference to all the planets then known to exist, the correspondence of the alleged law to the facts was remarkable. The one point in which the alleged system utterly failed was in requiring the existence of a planet to fill the gap between Mars and Jupiter. So boldly did Biela press his convictions of the correctness of this law upon the notice of his fellow-workers, that they resolved, in 1800, to divide the zodiac into twenty-four zones, to be apportioned among them, for the express purpose of searching for undiscovered planets. This well-organized effort was, erelong, rewarded by the surprising discovery of four new planets, the first one on the first night of the new century, January 1, 1801, and three more soon after. As no more seemed to be forthcoming, the search was relinquished in 1816. A fifth was found in 1845, and nearly five hundred since. Since 1891 photography has been wondrously serviceable in finding these bodies. A sensitive plate, on being exposed toward that part of the sky which it is desired to examine, will record all the perceptible stars as round disks; while any planets that appear in the field of view will, by their motion, leave their trace in the form of elongated trails or streaks, thus betraying themselves at once on the photographs. In this way Charlois, of Nice, Italy, has found nearly ninety small planets. All these planetoids, as the minor planets are often termed, are quite small, being but twenty to one hundred miles in diameter, and not consequential members of the solar system. Bode’s law thus fulfilled its temporary mission; but egregiously failed when Neptune claimed admission to a place in the solar system, for its distance from the sun was utterly out of harmony with that required by the law of Bode.

III. HOW NEPTUNE WAS FOUND.

The patience of Job had a strong parallel in the labors of those tireless toilers to whose minute computations we owe our knowledge of Neptune’s path in the skies. For this far-off planet was discovered not by the use of a telescope, or any optical instrument, but simply by a process of mathematical reasoning. The story is simply this. For sixty years after Uranus was recognized, there were irregularities in its motion that could not be satisfactorily accounted for. In the orbit that it was believed to pursue, it was sometimes in advance of its proper position, and sometimes it seemed to fall behind. Sometimes it appeared to be drawn a little to the right, and at other times as far the other way.

The thought at last came separately to several penetrating minds, not that the observations of its position were in error, but that Uranus must be drawn away from its supposed path by the attraction exercised upon it by some unseen body. And if such an object existed, was it a planet? Where was it? How large was it? What was its path in the far-off ether?

In the year 1842, the Royal Society of Sciences of Göttingen proposed as a prize question the full discussion of the theory of the motions of Uranus. It was specially sought to learn the cause of the large and increasing error of Bouvard’s Tables that had been relied upon to show its motion and its precise position at any time. Several able mathematicians undertook this intricate problem. Among them were John C. Adams, of Cambridge University, England, Sears C. Walker, of Washington, a man whose sad fate it was to pass away ere his magnificent abilities could receive extended recognition, and M. Le Verrier, of Paris. Working unknown to each other, they reached similar conclusions almost at the same time. Though not the first to solve the problem, the brilliant Frenchman was the first to announce his result, which he did by writing a letter to Dr. Galle, of the Berlin Observatory, where there was one of the largest telescopes in Europe, and asking him to search for his computed planet, and assigning its supposed place in the heavens. The very night he received the letter Dr. Galle found the planet within one degree of the point designated. The next night it had moved one minute of space, and was also seen to have a perceptible disk. This settled the question, and stamped it as a planet. Le Verrier well merited the title bestowed upon him, “First astronomer of the age.”

IV. METEORITES.

The nineteenth century will be forever memorable for its witnessing the closing career and final destruction of a famous comet. First noticed in France, in 1772, and rediscovered, in 1826, by an Austrian officer named Biela, it bears his name. His computation showed that it traversed its orbit in six and one half years. When it reappeared in 1846, and again in 1852, it was seen to have split into two unequal fragments. It has not been seen since; but at every time when its return should have taken place the earth has passed through showers of meteors supposed to be its constituent particles, and to indicate its entire disintegration.

During the meteoric shower of 1885, on the 27th of November, a large iron meteorite fell in Mazapil, Mexico, and chemical and physical investigation joined to pronounce it a part of the lost Biela’s comet.

The large cabinets of the world contain hundreds of specimens of meteorites, known to be such by their chemical composition, but only a few have actually been seen to fall. The most remarkable fall ever witnessed was that of May 10, 1879, in Iowa, in which the heaviest stone weighed 437 pounds. On April 8, 1893, an aerolite fell near Osawatomie, Kansas, and struck the monument to John Brown that had been erected through the efforts of Horace Greeley in 1863. The meteor broke off the left arm of the statue. A Texas meteorite, owned by Yale University, weighs 1635 pounds. A meteorite that fell in Jiminez, in 1892, now deposited in the city of Mexico, weighs twenty tons; and one lying on the coast of Labrador, which it is proposed to bring to the United States, is said to be still more massive.

V. DO METEORS OFTEN STRIKE THE EARTH?

It must not be thought that meteors usually strike the earth. In truth, but few of them do. The earth is surrounded by them, cold, dark, invisible, because unillumined. It is only when they become heated by rapidly impinging on the atmosphere that they can be seen at all; and unless they come near enough to become subject to the dominant power of the earth’s attraction, they pass off into space unnoticed, and their presence unsuspected.

A case in point is the brilliant “fire-ball” of July 20, 1860, that moved rapidly over the United States, from Wisconsin to Cape Cod, and then passed off into the skies. The entire time of its visible flight over a path of thirteen hundred miles was about two minutes. It was seen about ten o’clock in the evening. It was estimated to be from one hundred to five hundred feet in diameter, allowing for an increase as it expanded by reason of its striking with such velocity the lower and denser layers of the air. Its size and brilliancy were such as to arrest the attention of hundreds of persons, some of whom crouched in fear, and even alleged that they heard it hiss as it flew over their heads. Some fishermen in Lake Huron had ropes over the sides of their boat, ready to spring into the water if it came too near.

James H. Coffin, LL. D., then Professor of Astronomy in Lafayette College, made an exhaustive study of this unusual phenomenon, and, under the patronage of the Smithsonian Institution, published a volume containing many observations that he collected, with the mathematical results derived from them. Professor J. Hann, of Vienna, the highest authority on this subject, said that it was the most comprehensive study of a meteor’s path ever accomplished. Six years were spent in making the computations.

Self-illumined by the heat evolved in striking the various layers of the earth’s atmosphere, it became sufficiently bright to be first seen when seventy miles above the surface of the earth. It was within forty miles of touching us at the time it was over the Hudson River, when the great heat acquired by its rapid transit caused it to burst into two masses, which—like Biela’s comet—continued to pursue separate courses, side by side, until they were lost to view in their ascending flight, being last seen from the deck of a vessel off the island of Nantucket.

No part of the fire-ball struck the earth. Its orbit was an hyperbola, a curve not often found in nature, such that it can never come near us again unless, by the superior attraction of some celestial body, its course may be changed, and a new orbit result.

VI. ASTRONOMICAL OBSERVATORIES.

The Royal Observatory, at Greenwich, England, was founded by Charles the Second in 1675. Its main purpose was to extend astronomical knowledge, so that navigators might better find the position of their ships at sea. This institution retains its prominence. All the longitudes on our maps are reckoned from it, and Greenwich time is used on every ship that traverses the ocean. The “Nautical Almanac,” issued by the Observatory, was an indispensable part of the outfit of every sea captain until, in 1852, the United States provided its own American Ephemeris, a collection of tables of the motions and places of the sun, moon, and planets for every day and hour, and occultations of the stars, with rules for calculating longitude and the like.

Many valuable observations of the transit of Venus in 1769 were made at points near Philadelphia; but almost seventy years ensued before America witnessed the erection of any permanent buildings devoted to the purposes of this science.

President John Quincy Adams, who was highly versed in science, and held the position of president of the American Academy of Arts and Sciences in Boston for twenty years, often urged this matter on the attention of Congress, but without success.

President Thomas Jefferson, who was also a man of no small scientific information, as evidenced in his keeping a systematic weather record at his home in Monticello, Virginia, proposed an elaborate survey of the national coast. This was authorized by Congress in 1807. In the year 1832, in reviving an act for the continuance of the Coast Survey, Congress was careful to append the proviso “that nothing in the act should be construed to authorize the erection or maintenance of a permanent astronomical observatory.”

The expected return of Halley’s comet in 1835 again stimulated popular interest in the science, and aroused an intense desire to provide serviceable instruments, and to establish buildings suitable for their care and use. To Williams College, Massachusetts, belongs the honor of erecting, in 1836, the first astronomical observatory on this continent. Under its revolving dome was mounted an Herschelian telescope of ten feet focus, which later became the property of Lafayette College, where it is still preserved. In 1843, John Quincy Adams laid the corner-stone of the Longworth Observatory in Cincinnati, and delivered a commemorative address, his last great oration. The construction of the United States Naval Observatory at Washington soon followed, and before 1850 there were fourteen observatories established in this country. Nearly all the instruments they contained were made abroad, chiefly in Munich and London. Since then the number has risen to two hundred recognized observatories, of which twenty-four are of superior order, where systematic work is daily pursued, and the results are regularly published in book form. About two hundred observatories exist in other nations.

VII. IMPROVED INSTRUMENTS; THEIR EFFECT ON THE SCIENCE.

The great improvements in telescopes made during the century have been fruitful in two ways; a better knowledge of the surface of the moon and of the planets has been gained, and we have been enabled to learn with precision the exact motions and times of revolution of these bodies and of their accompanying moons. This information, by the use of the laws ascertained by Kepler and La Place, gives us their exact distance, dimensions, and mass. With the increase of telescopic power, the census of the starry host has been so augmented that the number of stars within reach of our modern instruments exceeds 125,000,000. But we had gone little beyond this sort of information until the invention of the spectroscope.

Previous to the year 1859 a few meteors, composed chiefly of stone or iron, some of which had been actually seen to fall from the sky, had been subjected to chemical analysis; but outside of this naught was known of the physical constitution of other worlds than ours. Our ignorance on this point was complete. All our attempts to become better acquainted with the structure of the planets, the composition of the sun, and the nature of the fixed stars would probably have been in vain but for the invention of the spectroscope. This surprising instrument is a master-key with which to unlock many of Nature’s mysteries; her recesses are brought to view, and the farthest star is subjected to an accurate chemical analysis, so far as the light that comes from it is sufficient to disclose the materials of which it is composed.

The wondrous use of electricity as an agent for the production of light, heat, and power is no greater achievement, in its way, than is Spectrum Analysis in bringing to our earthly laboratories the work of the Divine Hand performed in distant regions of space. Yet the story of the spectroscope is easily told. In its essential elements it is merely this: A ray of light, entering a darkened room through a hole in the window shutter, produces a bright beam on the opposite wall. A triangular glass prism held close to the crevice turns this beam into a band of rainbow hues. If the hole can be changed into a small slit, say one fourth of an inch high and one fiftieth of an inch wide, and if the light can further be made to pass in succession through several prisms, instead of through one, the band will be so elongated thereby that its various and surprising markings can be thoroughly traced and fully studied.

To this band of bright colors Sir Isaac Newton gave the name of the solar spectrum. The image formed by the light of any luminous body, after it has passed through a prism, is said to be the spectrum of that body.

VIII. THE SPECTROSCOPE AND ITS TRIUMPHS.

The spectroscope consists essentially of three tubes joined in the form of the letter Y, one of which is a small telescope, in the focus of which a narrow slit is placed to admit the ray of light that is to be examined; a prism, or a ruled grating that disperses the light, so as to form a spectrum; and a view telescope, with which to observe the various parts of the spectrum.

By using a small telescope to view the spectrum of the sun, Fraunhofer, a German optician, in 1814, discovered that the whole length of the spectrum was crowded with dark lines, very narrow, indeed, but scattered all through the seven hues. He found that sunlight, whether taken directly or reflected from clouds or from the moon or planets, invariably gave the same spectrum; but in no case did light from the stars give a spectrum of the same sort as that from the sun.

Dr. Kirchhoff, of Heidelberg, in 1859, explained the origin of the dark lines, and showed that there are three kinds of spectra: first, that of an incandescent solid or liquid, which is always perfectly continuous, showing neither dark lines nor bright; second, the spectrum of a glowing gas, which consists of bright lines or bands separated by dark spaces. These lines are characteristic of the chemical elements that cause them; and so, from the composition of the bright lines in a spectrum, it is possible to tell their origin. Third, a spectrum crossed by dark lines; which occurs when an incandescent solid is viewed through absorbent vapors.

In the solar eclipse of 1868, M. Janssen first noticed that the solar prominences gave a spectrum of the second kind, and thus proved that the prominences consist of glowing gas. Since that time the march of discovery has been exceedingly rapid.

This simple instrument has thus led the way to a knowledge of the elements composing every heavenly body, no matter what its distance, provided only it is giving out light intense enough to reach our gaze. For the perfection both of the telescope and spectroscope we owe much to the optical skill and mechanical dexterity of the Clarks and Rowland, Hastings and Brashear, all Americans.

About forty chemical elements have now been recognized in the sun. The most prominent are iron, calcium, hydrogen, nickel, and sodium. A distortion, or displacement, of some of the lines in the spectrum enables us to calculate the speed at which the gases are rushing toward or from us. A given line in the spectrum of Aldebaran is displaced toward the violet in such a way as to show that the star is approaching the sun at the rate of thirty miles a second; while a similar line, in the case of Altair, so deviates toward the red end of the spectrum as to prove that it is receding from the solar system at a velocity of twenty-four miles a second. By this principle, recognized by Doppler in 1842, the motions of about one hundred stars toward or from the solar system have been ascertained.

There is no question but that the solar system, as a whole, is steadily moving away from Sirius, and toward the constellation of Hercules; whether faster than at a rate of twelve miles every second is still scarcely decided; but this rate would be about a million miles a day, or three hundred and seventy million miles a year.

IX. WHAT IS DONE IN A LARGE OBSERVATORY; ITS WORK.

A visitor who wants to know what is done in a great observatory might go to Harvard some evening. He would probably find the large refractor pointed toward the satellites of Jupiter, Uranus, or Neptune, with a view of noting their precise places, so as to compute tables of their exact motions; or he might find a laborious observer watching such double stars as have considerable proper motion, and making drawings of conspicuous nebulæ, so that future astronomers may be able to decide whether time has wrought any changes in their constitution or figure. The great glass at Princeton, under the charge of Professor Charles A. Young, is largely used for spectroscopic work, examining the sun’s photosphere by day, and noting the spectra of the stars at night. Spectral observation is an important part of the routine at the Yerkes Observatory in Wisconsin.

Many faint comets have been successfully photographed at the Lick Observatory, on Mount Hamilton, California, and elsewhere by the use of very sensitive plates and a long exposure.

S. W. Burnham, of Chicago, is famed for his acuteness of vision, tested in having detected and measured over one thousand double stars which to other eyes had appeared only as single stars. The discovery of these objects belongs wholly to the nineteenth century; for in 1803, Sir William Herschel first announced the existence of sidereal systems composed of two stars, one revolving around the other, or both moving about a common centre. Some of these binary systems have periods of as great a length as fifteen hundred years; and some are as brief as four, and even two days. Some of them afford curious instances of contrasted colors, the larger star red or orange, and the smaller star blue or green.

X. THE NATIONAL OBSERVATORY AT WASHINGTON.

Professor William Harkness, U. S. N., M. D., LL. D., is widely known as the author of numerous astronomical and physical papers and books. He has also designed a number of instruments and made important discoveries. He has long been connected with the United States Naval Observatory, and now holds the position of Astronomical Director. His report for the year 1898 shows that the twenty-six inch reflector at Washington is now nightly engaged in mapping the relative positions of Rhea and Iapetus, the fifth and eighth satellites of Saturn, with the intention of securing a new and final determination of the mass of that planet, which has been heretofore reckoned as one 3492d of the sun. The twelve-inch telescope is chiefly employed in studying comets and asteroids, and on Thursday evenings is at the service of the public. In the year 1898, 3778 observations were made with the nine-inch transit circle, for which two men were detailed, with the services of five computers.

A transit circle and an altazimuth instrument, each turned out of solid steel, have recently been added to the equipment, and are of a workmanship that compares favorably with anything ever manufactured in Europe. It is asserted that the latter instrument will give more accurate measurements of declination than a transit circle, which is an innovation on long-cherished ideas.

Professor Simon Newcomb, of the United States Navy, is about to issue new tables of Mars, Uranus, and Neptune, and a “Catalogue of Fundamental Stars for the Epoch 1900.” During the year 1898 three thousand copies of the American Nautical Almanac were published. This is but an illustration of the scientific labor accomplished at this busy hive of industry. During the year this observatory issued to the navy 230 chronometers, 200 sextants and octants, and 1400 other nautical instruments of value.

XI. STAR MAPS AND CATALOGUES.

In the year 128 B. C. Hipparchus put out a catalogue of 1025 stars observed at Rhodes. Twenty such works succeeded this up to the year 1801, when Lalande, of Paris, brought out a list of 47,390 stars. It will be remembered that few stars have names, except those known to the Arabians of old, but are designated by their positions in the heavens. It is customary to refer to them by their declinations and right ascensions, as so many degrees north or south of the celestial equator, and so many degrees, or hours, east of the vernal equinox—fifteen degrees being the equivalent of an hour of right ascension—just like the latitude and longitude of cities on a common globe.

During the nineteenth century many celestial atlases and astronomical catalogues have been published. These contain lists of comets and nebulæ, and the places of the double stars and of the fixed stars. Of the latter alone over one hundred have appeared, of which Argelander’s is by far the largest, as it contains the places of more than 310,000 stars. The catalogue prepared by the British Association in 1845 is of great value, containing 8377 stars. Yarnall’s, of 10,658 stars, published in Washington in 1873, is most accessible to us.

Professor C. H. F. Peters, of the Hamilton College Observatory, Clinton, N. Y., the discoverer of so many asteroids, has prepared a valuable series of star charts. By dividing the heavens into small squares and carefully photographing each of them, the places of a vast number of stars can be recorded with far greater accuracy than by the old plan of a separate instrumental measurement of the position of the stars. By the use of microscopes the determination of their positions can be made with precision. These plates are preserved with care, and when those of the same region of the skies, made in different years, are compared, any variation in the relative positions of the objects can be detected with certainty. The perfection of this method of star-mapping is justly deemed one of the most important achievements of the century.

For an amateur star-gazer who is not provided with a set of maps, Whitall’s Planisphere is a very ready aid, as it can be instantly adjusted to any day and hour. The inexperienced, and those who have no instruments, can use it with ease and satisfaction to locate a thousand of the most conspicuous stars.

XII. ASTRONOMICAL BOOKS AND THEIR WRITERS.

In England this attractive study has been popularized chiefly by the interesting works of the two Herschels, who were voluminous writers, the lectures of Proctor, and the admirable compend of facts so assiduously gathered by G. F. Chambers in his delightful treatise on astronomy.

In our own country the heights of theoretical astronomy have been scaled by such minds as Benjamin Pierce, the profound mathematician of Harvard University; James C. Watson, of Ann Arbor, whose early death was a great loss to science; and Simon Newcomb, the genial savant of Washington. Chauvenet and Loomis have taught us the meaning of practical astronomy; and Olmsted, Young, Todd, and not a few others of distinction have prepared text-books that fully present the elements of the science.

Nor is this fascinating study limited to the students of the 484 colleges and universities of the land. The last report of the United States Commissioner of Education shows that in the public and private high schools of the nation there are over nine thousand boys and sixteen thousand girls pursuing the study of astronomy.

XIII. THE PRACTICAL USES OF ASTRONOMY AS AN AID TO NAVIGATION AND GEODESY.

The practical value of this science is best appreciated by the navigator, who sees in the sun and moon his clock, and in the stars and planets the ready means of learning his latitude and longitude. It is one of the first tasks of the midshipman to become familiar with the use of the sextant, by which he works out the problem of ascertaining the exact place of the ship upon the ocean. Navigation is helpless without the assistance of astronomy. Yet it is only the A, B, C of the science that the sailor has any use for; its higher mysteries are away beyond his needs and of no practical profit to him.

Nathaniel Bowditch, of Salem, Mass., in 1802, issued a book entitled “The New American Practical Navigator,” which is still a standard treatise for seamen. His rare acquirements as a mathematician were signally displayed, and in a form that has proved enduring, when, in 1814–17, he translated into English, accompanied with copious notes of his own, the profound work, “Celestial Mechanics,” penned by the gifted La Place in 1799. Although in name a translation of a foreign book with a commentary, it is in many respects an original work. Professor Elias Loomis, who left to Yale University three hundred thousand dollars as an endowment fund to aid in prosecuting astronomical research, said of him, in 1850, “Bowditch has probably done more for the improvement of physical astronomy than all other Americans combined.” Dr. Bowditch published the work in four ponderous quarto volumes wholly at his own private cost. These volumes he did not expose for sale, but generously gave them to such persons as proved to him their ability to appreciate and comprehend them. This outlay impaired the fortunes of his family, but became his own unique monument.

This work remains one of the most profound efforts of mathematical research on record. Bowditch’s accuracy has passed into a proverb. He gave the latitude of all the principal seaports of the world with marked precision; while some of the longitudes are now found to be slightly in error, it is surprising that his determinations of those of Boston and Philadelphia should be exactly the same as those obtained by the best methods in use to-day. But he makes San Francisco and Halifax seven miles too far to the east, and New York eight miles too far west. But we are to remember that for this computation the best available instruments were the chronometers of a century ago, and that lunar observations were made with the old-time sextant.

As applied to geodesy, astronomy has added a process of ascertaining geographical latitude with marvelous accuracy and speed by the use of the zenith telescope, an instrument devised by Major Talcott in 1835. This instrument can be set in a vertical direction with ease, and be pointed alternately to two stars that cross the meridian at a brief interval of time, the one north and the other south of the zenith. Difficulties that arise from refraction are avoided, and the resulting latitude is quickly computed. This method is largely employed in the surveys of the public lands, as also in establishing the boundary between the United States and British America.

XIV. NOTABLE EPOCHS IN THE NINETEENTH CENTURY.

Worth marking as epochs of the nineteenth century were such dates as October 10, 1846, when the first determination of difference of longitude of two places was made by the use of the telegraph wire. Sears C. Walker, in Washington, and E. Otis Kendall, in Philadelphia, compared their clocks by interchanging telegraphic signals, and thus found their respective longitudes.

In 1850, Professor William C. Bond, of Harvard College, invented the chronograph. Through the urgency of Sir David Brewster, it was shown in the great exhibition of that year in London, where a medal was awarded for it. The chronograph was speedily adopted throughout Europe, and together with other apparatus made by Bond constituted what there became known as the “American method” of recording observations. Through it the errors for which the “personal equation” is a partial remedy are largely eliminated, and a superior definiteness of record is obtained.

On August 7, 1869, the first application of the spectroscope to the examination of the corona of the sun was the beginning of the revelation of the inner mysteries of the constitution and activities of the great luminary. The transit of Venus that occurred on December 6, 1882, was fruitful in measurements, by which the estimates of the distance of the sun were reduced from the long-accepted figures, 95 to 92 millions of miles. Yet this loss of three millions of miles resulted from the apparently trifling change of reckoning the sun’s parallax at 8.82″, instead of 8.57″. An occurrence of vast practical advantage to the whole nation was that of November 18, 1883, when the four standard meridians of railroad time were adopted and put into use. From that day the clocks of the Union were set to keep either Eastern, Central, Mountain, or Pacific Coast time.

Professor Edward E. Barnard had used the magnificent telescope of thirty-six inches aperture, belonging to the Lick Observatory in California, but a short time before he astonished the world by discovering a fifth satellite of Jupiter, although it appeared as but a faint speck of light. Besides other honors for this achievement, in 1894 the French Academy of Sciences awarded him the Arago medal, of the value of a thousand francs, a distinction given but twice before, first to Le Verrier, for the discovery of Neptune in 1846, and to Asaph Hall, for finding the two moons of Mars in 1877.

“Personal equation” is the name given to the amount of error to which any person is habitually liable in attempting to note the time of a fixed occurrence. When the astronomer looks at a star passing the cross-wires of his transit, he is likely to make the record one or two tenths of a second after the true time, or possibly a like small amount of time before the actual occurrence, by anticipation. This is not a matter of wrong intention, nor due to willfulness. But in precise observations, especially where comparisons are to be made between the records of several persons, the “personal equation” must be determined, if possible, and allowed for. Various methods of correcting this inaccuracy have been used. But the best is that of Frank H. Bigelow, of the Nautical Almanac Office, Washington, who, in 1890, devised a process of taking star transits by photography. It entirely does away with this source of error, and has proved of great value.

XV. DISCARDED DOCTRINES AND ABANDONED IDEAS.

A few generations ago an eight-day clock was to be found only in the homes of well-to-do people, and a gold watch was a symbol of wealth, such as to subject its wearer to a special tax. In this age of dollar clocks and Waterbury watches, almanacs are no longer indispensable. We do not regulate our time-pieces by the rising and setting of the sun; nor can a future Jay Gould lay the foundation of his fortune, as did the one best known by that name, by setting up rural noon-marks for a fixed fee.

Some pleasant dreams of past decades have vanished in the light of recent knowledge. The nebular hypothesis, that wondrous conception of Swedenborg, elaborated by La Place and espoused by William Herschel and so many others, as affording a full explanation of the method by which our worlds were shaped into their present forms, has ceased to have general acceptance. M. Maedler, director of the Dorpat Observatory in 1846, had a firm persuasion that the collective body of stars visible to us has a movement of revolution about a centre situated in the group of the Pleiades, and corresponding to the star Alcyone. But this notion of a central sun around which all the solar system is circling has lost ground.

The distortion in the orbit of the planet Mercury has been accounted for by the urgent suggestion that there must be some planet, as yet undiscovered, that disturbs the regularity of Mercury’s movements, but whose orbit is so near to the sun as to baffle all ordinary efforts to see it. It has received, by anticipation, the prenatal name of Vulcan. Many eyes have peered most intently into the region indicated, and some few have imagined they had found what they sought. A physician of the village of Orgeres, France, M. Lescarbault by name, on March 20, 1859, saw such an object pass over the sun’s disk. The skillful Le Verrier was much impressed by this physician’s minute account of the occurrence. But there was no confirmation of the alleged discovery. At the time of subsequent eclipses that part of the heavens has been repeatedly examined closely, but in vain. So we must wait longer before believing that Vulcan does exist.

When, in 1877, Professor Hall, through the powerful telescope at Washington, saw that Mars was attended by two tiny satellites, he put a permanent injunction on the further use of the once favorite phrase,

And so of the question oft discussed in the old-time debating societies, “Are the planets inhabited?” It may still be left in the hands of young collegians, notwithstanding the fact that our largest telescopes give only negative testimony.

In a solar eclipse in February, 1736, that was annular in shape, just before the sun was completely hidden, the narrow horn of light seemed to break into a series of dots, or luminous points, which, when noted again a century later and described by Francis Baily, received the name of “Baily Beads.” It was attempted to explain this as caused by the moon’s mountains cutting off the last rays of sunlight, or else as produced by irradiation. But with the advent of stronger telescopic power the phenomenon has come to an end.

David Rittenhouse, of Norristown, whom Thomas Jefferson considered “second to no astronomer living,” built an orrery worth a thousand dollars, to illustrate mechanically the motions of all the planets, and though the instrument is still treasured in the University of Pennsylvania, and its duplicate at Princeton, among the relics of a past age, it is assigned to the category of toys. Mural circles, much depended upon to measure the declination of heavenly bodies, have fallen into disuse, supplanted by improved transit instruments.

XVI. PROBLEMS FOR FUTURE STUDY.

Many problems are in store for the future. The field for research still opens wide. How the solar activity is to be maintained was answered by Newton in the suggestion that comets falling into it kept up its supply of matter and energy. Waterston, in 1853, propounded the thought that meteoric matter may be the aliment of the sun. Now the prevalent theory is that a contraction of the sun’s volume, constantly in progress, but so slight as to be invisible to the most powerful telescope, is competent to furnish a heat supply equal to all that can have been emitted during historic periods.

Professor Newcomb answers the question, “How long will the sun endure?” by saying, “The physical conclusion to which we are led by a study of the laws of nature is that the sun, like a living being, must have a birth and will have an end. From the known amount of heat which it radiates we can, even in a rude way, calculate the probable length of its life. From fifteen to twenty millions of years seems to be the limit of its age in the past, and it may exist a few millions of years, perhaps five or ten, in the future.”