Part 11

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.

[Illustration: PROFESSOR WILLIAM HARKNESS,

Astronomical Director U. S. Naval Observatory, Washington, D. C.]

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.

[Illustration: ZENITH TELESCOPE.

Made for University of Pennsylvania by Warner & Swasey.]

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,

“The snowy poles of moonless Mars.”

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.

[Illustration: THREE-INCH TRANSIT, BY WARNER & SWASEY.]

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.”

[Illustration: CAROLUS LINNÆUS OF SWEDEN, FATHER OF MODERN BOTANY.

This illustration was prepared by a Swedish society, and represents the famous botanist after his return from the exploration of Lapland, and with a bunch of his favorite flower (_Linnæa borealis_) in his hand. ]

STORY OF PLANT AND FLOWER

BY THOMAS MEEHAN,

_Vice President Academy of Natural Sciences, Philadelphia_.

Botany, in its general sense, signifies the knowledge of plants. In the earlier periods of human history plants appealed to mankind as material for food or medicine; and down to comparatively recent times botanical studies were pursued mainly in these directions. Dioscorides, a Greek, who lived in the first century of the Christian era, is the earliest writer of whom we have knowledge that can lay a claim to botanical distinction, but the medical property of plants was evidently the chief incentive to his task. It was not until the beginning of the sixteenth century that botany, in its broad sense, became a study, and Le Cluse, a French physician, who died in 1609, may be regarded as one of its patriarchs. Still the medical uses of plants were steadily kept in view. The English botanist, John Gerarde, who was a contemporary of Le Cluse, or Clusius, as botanists usually call him, wrote a remarkable work on botany,—remarkable for his time,—but this was styled a “Herbal,” as were other famous botanical works down to the beginning of the present century.

Following the year 1700, the knowledge of plants individually became so extended that systematic arrangement became desirable. The first real advance in this direction was made by Carl Von Linné, commonly known by its Latin form, Linnæus, a Swede, born in 1707, and whose talents for botanical acquirements seemed almost innate. In his twenty-third year he saw the need of a better system, and commenced at once the great work of botanical reform. He saw that plants with a certain number of stamens and pistils were correlated, and he founded classes and orders on them. Flowers with five stamens or six stamens would belong to his class pentandria or hexandria, respectively, and those with five pistils or six pistils pentagynia, or hexagynia, accordingly; and so on up to polyandria, or polygynia—many stamens or pistils—of which our common buttercup is an illustration. He further showed that two names only were all that is necessary to denote any plant, the generic name and its adjective, as, for instance, _Cornus alba_, the white Dogwood; and that the descriptions should be brief, covering only the essential points wherein one species of plant differed from another. This became known as the sexual system. It fairly electrified intelligent circles. People generally took to counting stamens and pistils, and large numbers took pride in being botanists because they could trace so easily the classes and orders of the plants they met. The grand old man died in 1778, and though his artificial system had to give way to a more natural method, he is justly regarded as the father of modern botany.

[Illustration: THE GREEN ROSE.

Flower with leaves for petals.]

With the incoming of the nineteenth century, botany took a rapid start. It ceased to be a mere handmaid to the study of medicine. Chemistry, geography, teleology, and indeed the chief foundations of biology had become closely interwoven with botanical studies; and thus the progress of botany through the century has to be viewed from many standpoints.

In classification, what is known as the natural system has replaced the sexual. Plants are grouped according to their apparent relationships. Those resembling in general character the Rose form the order _Rosaceæ_; the Lily, _Liliaceæ_. Sometimes, however, a striking characteristic is adopted for the family name, as _Compositæ_, or compound flower, for the daisy and aster-flowered plants; _Umbelliferæ_, or umbel-flowering, as in carrot or parsley; _Leguminosæ_, having the seed vessels as legumes, like peas and beans.

[Illustration: HEAD OF WHITE CLOVER, WITH A BRANCH FROM THE CENTRE.]