The Great Events by Famous Historians, Volume 17 · Chapter 9Disunion in America (3)
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From the time of Sir William Herschel the science of stellar astronomy, revealing the enormous distances of the stars—none of them really fixed, but all having real or apparent motions—was rapidly developed. The discovery of stellar planets, at almost incalculable distances, still further changed the aspect of the heavens as viewed by astronomers, and when the capital discovery of Neptune was made those men of science were well prepared for studying its nature and importance. These matters, as well as the simultaneous calculation of the place of Neptune by Adams and Leverrier, and its actual discovery by Galle, are set forth by Sir Oliver Lodge in a manner as charming for simplicity as it is valuable in its summary of scientific learning.
The explanation by Newton of the observed facts of the motion of the moon, the way he accounted for precession and nutation and for the tides; the way in which Laplace explained every detail of the planetary motions—these achievements may seem to the professional astronomer equally, if not more, striking and wonderful; but of the facts to be explained in these cases the general public is necessarily more or less ignorant, and so no beauty or thoroughness of treatment appeals to it or excites its imagination. But to predict in the solitude of the study, with no weapons other than pen, ink, and paper, an unknown and enormously distant world, to calculate its orbit when as yet it had never been seen, and to be able to say to a practical astronomer, "Point your telescope in such a direction at such a time, and you will see a new planet hitherto unknown to man"—this must always appeal to the imagination with dramatic intensity, and must awaken some interest in the dullest.
Prediction is no novelty in science; and in astronomy least of all is it a novelty. Thousands of years ago Thales, and others whose very names we have forgotten, could predict eclipses, but not without a certain degree of inaccuracy. And many other phenomena were capable of prediction by accumulated experience. A gap between Mars and Jupiter caused a missing planet to be suspected and looked for, and to be found in a hundred pieces. The abnormal proper-motion of Sirius suggested to Bessel the existence of an unseen companion. And these last instances seem to approach very near the same class of prediction as that of the discovery of Neptune. Wherein, then, lies the difference? How comes it that some classes of prediction—such as that if you put your finger in fire it will be burned—are childishly easy and commonplace, while others excite in the keenest intellects the highest feelings of admiration? Mainly, the difference lies, first, in the grounds on which the prediction is based; second, in the difficulty of the investigation whereby it is accomplished; third, in the completeness and the accuracy with which it can be verified. In all these points, the discovery of Neptune stands out as one among the many verified predictions of science, and the circumstances surrounding it are of singular interest.
Three distinct observations suffice to determine the orbit of a planet completely, but it is well to have the three observations as far apart as possible so as to minimize the effects of minute but necessary errors of observation. When Uranus was found old records of stellar observations were ransacked with the object of discovering whether it had ever been unwittingly seen before. If seen, it had been thought, of course, to be a star—for it shines like a star of the sixth magnitude, and can therefore be just seen without a telescope if one knows precisely where to look for it and if one has good sight—but if it had been seen and catalogued as a star it would have moved from its place, and the catalogue would by that entry be wrong. The thing to do, therefore, was to examine all the catalogues for errors, to see whether the stars entered there actually existed, or whether any were missing. If a wrong entry were discovered, it might of course have been due to some clerical error, though that is hardly probable considering the care spent in making these records, or it might have been a tailless comet, or possibly the newly found planet.
The next thing to do was to calculate backward, to see whether by any possibility the planet could have been in that place at that time. Examined in this way the tabulated observations of Flamsteed showed that he had unwittingly observed Uranus five distinct times; the first time in 1690, nearly a century before Herschel discovered its true nature. But more remarkable still, Le Monnier, of Paris, had observed it eight times in one month, cataloguing it each time as a different star. If only he had reduced and compared his observations, he would have anticipated Herschel by twelve years. As it was, he missed it. It was seen once by Bradley also. Altogether it had been seen twenty times.
These old observations of Flamsteed and those of Le Monnier, combined with those made after Herschel's discovery, were very useful in determining an exact orbit for the new planet, and its motion was considered thoroughly known. For a time Uranus seemed to travel regularly, and as expected, in the orbit which had been calculated for it; but early in the present century it began to be slightly refractory, and by 1820 its actual place showed quite a distinct discrepancy from its position as calculated with the aid of the old observations. It was thought at first that this discrepancy must be due to inaccuracies in the older observations, and they were accordingly rejected, and tables prepared for the planet based on the newer and more accurate observations only. But by 1830 it became apparent that it did not coincide with even these. The error amounted to about 20". By 1840 it was as much as 90", or a minute and a half. This discrepancy is quite distinct, but still it is very small; and had two objects been in the heavens at once, the actual Uranus and the theoretical Uranus, no unaided eye could possibly have distinguished them or detected that they were other than a single star.
The errors of Uranus, though small, were enormously greater than other things which had certainly been observed; there was an unmistakable discrepancy between theory and observation. Some cause was evidently at work on this distant planet, causing it to disagree with its motion as calculated according to the law of gravitation. If the law of gravitation held exactly at so great a distance from the sun, there must be some perturbing force acting on it besides all the known forces that had been fully taken into account. Could it be an outer planet? The question occurred to several, and one or two tried to solve the problem, but were soon stopped by the tremendous difficulties of calculation.
The ordinary problem of perturbation is difficult enough: Given a disturbing planet in such and such a position, to find the perturbations it produces. This was the problem that Laplace worked out in the Mécanique Céleste.
But the inverse problem—given the perturbations, to find the planet that causes them—such a problem had never yet been attacked, and by only a few had its possibility been conceived. Friedrich Bessel made preparations for solving this mystery in 1840, but he was prevented by fatal illness.
In 1841 the difficulties of the problem presented by these residual perturbations of Uranus excited the imagination of a young student, an undergraduate of Cambridge—John Couch Adams by name—and he determined to make a study of them as soon as he was through his tripos. In January, 1843, he was graduated as senior wrangler, and shortly afterward he set to work. In less than two years he reached a definite conclusion; and in October, 1845, he wrote to the astronomer-royal, at Greenwich, Professor Airy, saying that the perturbations of Uranus could be explained by assuming the existence of an outer planet, which he reckoned was now situated in a specified latitude and longitude.
We know now that had the astronomer-royal put sufficient faith in this result to point his big telescope at the spot indicated and begin sweeping for a planet, he would have detected it within 1-3/4º of the place assigned to it by Adams. But anyone in the situation of the astronomer-royal knows that almost every post brings absurd letters from ambitious correspondents, some of them having just discovered perpetual motion, or squared the circle, or proved the earth flat, or discovered the constitution of the moon or of ether or of electricity; and in this mass of rubbish it requires great skill and patience to detect such gems of value as may exist.
Now this letter of Adams's was indeed a jewel of the first water, and no doubt bore on its face a very different appearance from the chaff of which I have spoken; but still Adams was unknown: he had been graduated as senior wrangler, it is true, but somebody must be graduated as senior wrangler every year, and a first-rate mathematician is not produced every year. Those behind the scenes—as Professor Airy of course was, having been a senior wrangler himself—knew perfectly well that the labeling of a young man on his taking his degree is much more worthless as a testimony to his genius and ability than the general public is apt to suppose.
Was it likely that a young and unknown man should have solved so extremely difficult a problem? It was altogether unlikely. Still, he should be tested: he should be asked for explanations concerning some of the perturbations which Professor Airy had noticed, and see whether he could explain these also by his hypothesis. If he could, there might be something in his theory. If he failed—well, there was an end of it. The questions were not difficult. They concerned the error of the radius vector. Adams could have answered them with perfect ease; but sad to say, though a brilliant mathematician, he was not a man of business. He did not answer Professor Airy's letter.
It may seem a pity to many that the Greenwich equatorial was not pointed at the place, just to see whether any foreign object did happen to be in that neighborhood; but it is no light matter to derange the work of an observatory, and alter the plans laid out for the staff, into a sudden sweep for a new planet on the strength of a mathematical investigation just received by post. If observatories were conducted on these unsystematic and spasmodic principles they would not be the calm, accurate, satisfactory places they are.
Of course, if anyone had known that a new planet was to be found for the looking, any course would have been justified; but no one could know this. I do not suppose that Adams himself felt an absolute confidence in his attempted prediction. So there the matter dropped. Adams's communication was pigeonholed, and remained in seclusion eight or nine months.
Meanwhile, and quite independently, something of the same sort was going on in France. A brilliant young mathematician, Urban Jean Joseph Leverrier, born in Normandy in 1811, held the post of astronomical professor at the École Polytechnique, founded by Napoleon. His first published papers directed attention to his wonderful powers; and the official head of astronomy in France, the famous Arago, suggested to him the unexplained perturbations of Uranus as a worthy object for his fresh and well-armed vigor. At once he set to work in a thorough and systematic way. He first considered whether the discrepancies could be due to errors in the tables or errors in the old observations. He discussed them with minute care, and came to the conclusion that they were not thus to be explained away. This part of the work he published in November, 1845.
He then set to work to consider the perturbations produced by Jupiter and Saturn to see whether they had been accurately allowed for, or whether some minute improvements could be made sufficient to destroy the irregularities. He introduced several fresh terms into these calculations, but none of them of sufficient importance to do more than partly explain the mysterious perturbations. He next examined the various hypotheses that had been suggested to account for them. Were they caused by a failure in the law of gravitation or by the presence of a resisting medium? Were they due to some large but unseen satellite or to a collision with some comet?
All these theories he examined and dismissed for various reasons. The perturbations were due to some continuous cause—for instance, some unknown planet. Could this planet be inside the orbit of Uranus? No, for then it would perturb Saturn and Jupiter also, and they were not perturbed by it. It must, therefore, be some planet outside the orbit of Uranus, and in all probability, according to Bode's empirical law, at nearly double the distance from the sun that Uranus is. Finally he proceeded to determine where this planet was, and what its orbit must be to produce the observed disturbances.
Not without failures and disheartening complications was this part of the process completed. This was, after all, the real tug of war. Many unknown quantities existed: its mass, its distance, its eccentricity, the obliquity of its orbit, its position—nothing was known, in fact, about the planet except the microscopic disturbance it caused in Uranus, several thousand million miles away from it. Without going into further detail, suffice it to say that in June, 1846, he published his last paper, and in it announced to the world his theory as to the situation of the planet.
Professor Airy received a copy of this paper before the end of the month, and was astonished to find that Leverrier's theoretical place for the planet was within 1° of the place Adams had assigned to it eight months before. So striking a coincidence seemed sufficient to justify a Herschelian sweep for a week or two. But a sweep for so distant a planet would be no easy matter. When seen through a large telescope it would still only look like a star, and it would require considerable labor and watching to sift it out from the other stars surrounding it. We know that Uranus had been seen twenty times, and thought to be a star, before its true nature was discovered by Herschel; and Uranus is only about half as far away as Neptune.
Neither at Paris nor at Greenwich was any optical search undertaken; but Professor Airy wrote to ask M. Leverrier the same old question that he had fruitlessly put to Adams: Did the new theory explain the errors of the radius vector or not? The reply of Leverrier was both prompt and satisfactory—these errors were explained, as well as all the others. The existence of the object was then for the first time officially believed in. The British Association met that year at Southampton, and Sir John Herschel was one of its sectional presidents. In his inaugural address, on September 10, 1846, he called attention to the researches of Leverrier and Adams in these memorable words:
"The past year has given to us the new [minor] planet Astræa; it has done more—it has given us the probable prospect of another. We see it as Columbus saw America from the shores of Spain. Its movements have been felt trembling along the far-reaching line of our analysis with a certainty hardly inferior to ocular demonstration."
It was nearly time to begin to look for it. So the astronomer-royal thought on reading Leverrier's paper. But as the national telescope at Greenwich was otherwise occupied, he wrote to Professor Challis, at Cambridge, to know whether he would permit a search to be made for it with the Northumberland equatorial, the large telescope at Cambridge University, presented to it by one of the Dukes of Northumberland.
Professor Challis said he would conduct the search himself, and shortly began a leisurely and dignified series of sweeps around the place designated by theory, cataloguing all the stars he observed, intending afterward to sort out his observations, compare one with another, and find out whether any one star had changed its position; because if it had it must be the planet. Thus, without giving an excessive time to the business, he accumulated a host of observations.
Professor Challis thus actually saw the planet twice—on August 4 and August 12, 1846—without knowing it. If he had had a map of the heavens containing telescopic stars down to the tenth magnitude, and if he had compared his observations with this map as they were made, the process would have been easy and the discovery quick. But he had no such map. Nevertheless one was in existence. It had just been completed in that country of enlightened method and industry—Germany. Doctor Bremiker had not indeed completed his great work—a chart of the whole zodiac down to stars of the tenth magnitude—but portions of it were completed, and the special region where the new planet was expected to appear happened to be among the portions finished. But in England this was not known.
Meanwhile Adams wrote to the astronomer-royal several additional communications, making improvements in his theory, and giving what he considered nearer and nearer approximations for the place of the planet. He also now answered quite satisfactorily, but too late, the question about the radius vector sent to him months before.
Leverrier was likewise engaged in improving this theory and in considering how best the optical search could be conducted. Actuated probably by the knowledge that in such matters as cataloguing and mapping Germany was then, as now, far ahead of all the other nations, he wrote in September (the same year that Sir John Herschel delivered his eloquent address at Southampton) to Berlin. Leverrier wrote to Doctor Galle, head of the observatory at Berlin, saying to him, clearly and decidedly, that the new planet was now in or close to such and such a position, and that if he would point his telescope to that part of the heavens he would see it; and moreover that he would be able to tell it from a star by its having a sensible magnitude, or disk, instead of being a mere point.
Galle got the letter on September 23, 1846. That same evening he pointed his telescope to the place Leverrier told him, and saw the planet. He recognized it first by its appearance. To his practised eye it did seem to have a small disk, and not quite the same aspect as an ordinary star. He then consulted Bremiker's great star-chart, the part just engraved and finished, and, sure enough, no such star was there. Undoubtedly it was the planet.
The news flashed over Europe at the maximum speed with which news could travel at that date (which was not very fast); and by October 1st Professor Challis and Mr. Adams heard it at Cambridge, and realized that in so far as there was competition in such a matter England was out of the race.
It was an unconscious race to all concerned, however. The French scientists knew nothing of the search in England. Adams's papers had never been published; and very annoyed the French were when a claim was set up in his behalf to a share in this magnificent discovery. As for Adams himself, we are told that by no word did he show resentment at the loss of the practical consummation of his discovery. His part in any controversy that arose was calm and dignified; but for a time his friends fought a public battle for his fame. It so happened that the public took a keener interest than it usually takes in scientific predictions; but the discussion has now settled down. All the world honors the bright genius and mathematical skill of John Couch Adams, and recognizes that he first solved the problem by calculation. All the world, too, perceives clearly the no less eminent mathematical talents of M. Leverrier, but it recognizes in him something more than the mere mathematician—the man of energy, decision, and character.
(1846) THE ACQUISITION OF CALIFORNIA, Henry B. Dawson
In the history of the United States, the acquisition of California, carrying with it that of New Mexico, was a peculiar and unusual event, and one of immense significance in the expansion and development of the Republic. Together with the annexation of Texas, it was the most important result of the Mexican War. The California country, formerly an indeterminate territory of vast extent, was settled by Spanish missionaries in the seventeenth century. Their settlements within the present limits of the State of California date from the first foundation of San Diego in 1769. In 1822 the entire region called California became a part of the Mexican Republic, and it remained a possession of Mexico until the time of the transfer described below.
At the beginning of 1846 the population of California included, with about two hundred thousand Indians, six thousand Mexicans and perhaps two hundred Americans. War against Mexico had been declared in May, 1845, and already General Taylor had won the battles of Palo Alto and Resaca de la Palma, and had compelled the surrender of Monterey. While these operations were leading the United States forces to the rapid accomplishment of their work in Mexico proper, other movements were undertaken, the execution and outcome of which form the subject of Mr. Dawson's narrative. In 1848 California and New Mexico were ceded to the United States.
Immediately after the opening of hostilities in the valley of the Rio Grande (March, 1846), among the expeditions which were organized by the Federal authorities was one to move against and take possession of California and New Mexico, two provinces in the northern part of the enemy's country. The command of this expedition had been vested in General Stephen W. Kearney, and the force under his command had rendezvoused at Fort Leavenworth; and the most energetic measures had been adopted to insure its early departure and its ultimate success.
Having completed all the arrangements, on June 26th the main body of this expedition had moved from the fort; and after a rapid but interesting march of eight hundred seventy-three miles, on August 18th it entered and took possession of Santa Fé, the capital of New Mexico, the Mexican forces, numbering four thousand, which had been collected to defend the town, having dispersed, without offering the least opposition, as it approached.
While these operations in New Mexico and on the western frontier of the United States were taking place, Brevet-Captain John C. Frémont, who had been engaged in explorations on the western slope of the Rocky Mountains, had also revolutionized the Province of California, and, to some extent at least, had anticipated the movements of the expedition commanded by General Kearney. The character of his mission being scientific and peaceful rather than warlike, he had not had an officer or soldier of the regular army in his company; and his whole force had consisted of sixty-two men employed by himself for security against the Indians and for procuring subsistence in the wilderness and desert country through which he had passed. For the purpose of obtaining game for his men and grass for his horses, in an uninhabited part of California, he had, during the winter of 1845-1846, solicited and obtained permission from the Mexican authorities to winter in the Valley of San Joaquin; but he had scarcely established himself before he received advices that the Mexican commander was preparing to attack him under the pretext that under the cover of a scientific mission he was exciting the American settlers in that vicinity to revolt.
In view of this threatened attack, and for the purpose of repelling it, Lieutenant Frémont immediately occupied a mountain which overlooked Monterey—although it was thirty miles from that city—and having intrenched it and raised the flag of the United States he waited the approach of the enemy. After remaining there until March 10, 1846, he retired to the northward, intending to march, by way of Oregon, to the United States; but about the middle of May, after he had quietly passed into Oregon, he had received information through Samuel Neal and Levi Sigler, two hunters who had been sent after him from Lassen's rancho, that the Mexican Governor of California was pursuing him, while the Indians, by whom he was surrounded, instigated by the enemy, had shown signs of hostility, and had killed or wounded five of his men.
Under these circumstances, on June 6, 1846, Lieutenant Frémont had resolved to turn on his pursuers with the little party under his command, and to seek safety, not merely in the overthrow of his pursuers, but in that of the entire Government of Mexico in the Province of California. Accordingly, on June 11th, Lieutenant Frémont, assisted by Captain Merritt and fourteen of the settlers, had attacked and captured an escort of horses destined for General Castro's troops—Lieutenant Arce, fourteen men, and two hundred horses remaining in his hands as the trophies of his victory. On the 15th the military post of Sonoma was surprised, and General Vallejo, Captain Vallejo, Colonel Greuxdon and several other officers, nine pieces of brass cannon, two hundred fifty stands of muskets, and other stores and arms were taken; and on the 25th the military commandant of the Province, who had moved toward the post with a heavy force to retake it, was attacked by Lieutenant Frémont and twenty men, and completely routed. Having thus cleared that part of the Province north of the Bay of San Francisco of the enemy, it is said that on July 5th Captain Frémont had assembled the American settlers at Sonoma, addressed them upon the dangers of their situation, and recommended a declaration of independence and war on Mexico as the only remedy; and that the hardy frontiersmen promptly accepted the proposal and raised the flag of independent California—a bear and a star on a red ground.
While these revolutionary movements were destroying the power of Mexico in the interior of the Province of California, and the expedition under General Kearney—ignorant of the fact that the work had been done already—was approaching its eastern borders for the same purpose, the naval force of the United States in the Pacific, under Commodore Sloat, had been assisting in the work of conquest. Having heard of the opening of hostilities on the Rio Grande, the Commodore—then at Mazatlan—hastened with the Savannah to Monterey in California, where he arrived on July 2d, and on the 7th he took possession of the town without opposition; the custom-house was seized, the American flag raised, and California declared to be "henceforward a part of the United States."
Within a few days intelligence of the action of Commodore Sloat was received by the revolutionary leaders at Sonoma; and a battalion of mounted riflemen which had been organized among them was immediately moved to Monterey, the flag of the United States was substituted for the "bear and star," and the authority of the Commodore was immediately recognized. This battalion of mounted riflemen on its arrival at Monterey, July 23, 1846, was mustered into the service of the United States by Commodore Stockton, who had succeeded Commodore Sloat in command of the squadron—Captain Frémont being appointed its commandant, and Lieutenant A. H. Gillespie, of the Marines, its second officer—and it was immediately despatched on the sloop-of-war Cyane to San Diego for the purpose of cutting off the retreat of General Castro, of the Mexican service, who had encamped and fortified his position near Ciudad de los Angeles, while the Commodore with his sailors—who landed from the Congress at San Pedro—moved against him in front. The expedition was eminently successful, as the Mexicans on the approach of the Commodore immediately evacuated their camp and fled in the greatest confusion—although most of the principal officers were subsequently captured—and, on August 13th, the Ciudad de los Angeles was occupied, again without opposition, by the American troops and seamen, and the conquest of California was apparently completed.
A short time afterward Commodore Stockton appointed Captain Frémont Governor of the Territory into which, by the proclamation of Commodore Sloat, the Province had been transformed; while Captain Gillespie was left, with nineteen men, in possession of Los Angeles; Lieutenant Talbot, of the Topographical Engineers, with nine men, was left at Santa Barbara; and, with his squadron, Commodore Stockton proceeded to San Francisco; while Governor Frémont, on September 8th, also moved to Monterey.
The main body had no sooner left Los Angeles than the Californians—who before the departure of the Commodore and the Governor had held secret meetings for the purpose—rose in arms for the expulsion of the invaders of their country. Indeed an attempt appears to have been intended before the Governor left the city; but, by timely precautions, it had been prevented; although the purpose and determination still continued and were called into requisition at a more convenient season. The necessary preparations having been made for that purpose under the directions of José Antonio Carrillo, a professed conspirator of that vicinity, at an early hour on the morning of September 23d, the quarters of Captain Gillespie were attacked by Cerbulo Varela—a metamorphosed captain under Governor Frémont—at the head of sixty-five men, under cover of a thick fog. The morning was auspicious for such purposes, yet the Captain was not surprised; and the twenty-one rifles which he controlled were quickly brought to bear on the assailants, who retired soon afterward with three of their number killed and several wounded; and at daylight the remainder were driven from the town, with the loss of several taken prisoners, by a few men under Lieutenant Hensley, and Doctor Gilchrist, of the navy.