MR. PROCTOR'S " ASTRONOMY."*
Tun late Mr. Proctor, it appears, planned his Old and New Astronomy a quarter-of-a-century ago, but in a more elaborate form, as he intended to devote separate treatises to the more important subjects. It became necessary, on the failure of a bank, however, to turn to lecturing and popular writing, and, moreover, he realised the indifference of the public to pro- found exposition and reasoning. His lecturing, Mr. Cowper Ranyard says, "afforded him an excellent training in the clearness and simplicity of expression that is needed for popu- lar exposition." What a busy leisure might have enabled Mr. Proctor to produce, no one can say, but perhaps it would not be rash to say that the gain in lucidity has balanced the loss of profundity ; for the Old and New Astronomy, as
* Old and New Astronomy. By Richard A. Proctor. Completed by A. Cowper 'lanyard. With numerous Plates and Woodcuts. Loudon: Longmans and Co.
it now stands, clear and striking though many of its explana- tions are, is not child's-play. Mr. Proctor himself had a mathematical mind, and he expected his readers to have reached a certain stage of mathematical knowledge and to know some of the fundamental physical laws. Now, the average reader is shamefully ignorant of some of the very first principles of physics, though they stare him or her in the face every minute of the day. Yet so simple and pointed is Mr. Proctor's style—at times it is beyond all praise—that we cannot conceive a person of the meanest intellect failing to grasp some valuable pieces of knowledge from this volume. Moreover, the mathematical demonstrations are ample enough, and frequent enough, to attract mathematicians to the descrip- tion of the many proofs of astronomical physics. It is a subject for lasting regret, however, that death prevented the completion of the work by its author. The Milky Way, the Star Clusters, and the Nebula) were subjects which would have shown Mr. Proctor's well-balanced judgment, and power of clear yet close reasoning at their very best. It was well known, indeed, that his best work was intended to be put into these last chapters. At the date of his death, the chapters on the planets were in manuscript, and Mr. Cowper Ranyard has striven to carry out the rest of the design to the full.
At the beginning, the observations of the Ancients are dis- cussed, and Mr. Proctor takes up a most positive attitude about the astronomical purpose of the Great Pyramid, though be does not by any means follow Professor Piazzi Smyth. We may remark, incidentally, that moderate as he is in putting forward his own opinion, and careful on the whole in weighing conflicting evidence and rival theories, Mr. Proctor is at no pains to hide his contempt of unsound hypotheses, and even of those astronomers who have been unable to grasp the significance of their own work. Towards the 01 WOXACII and those who, for instance, believe the earth to be flat, he professes a lofty toleration, and, though he condescends to expound for their benefit, beyond a certain point he dismisses them curtly. The Great Pyramid, he says, was built by astronomers for astronomers ; and while allowing the Egyptologist to be entitled to speak as to the partly sepulchral nature of the Pyramid, he denies his ability to speak as to its astronomical intention. Some one, it is true, must be positive about these things ; a little asser- tion is of great assistance, even to the cautious scientific habit of mind. The masonry of the Pyramid is a source of perpetual wonder to thoughtful people ; and its mathematical finish, and, in particular, the ingenious construction of the Grand Gallery, are circumstantial evidences of an over- whelming nature. The device by which the sides were made accurate for observation, and yet subservient to the exigencies of mechanics in being wider at the bottom than at the top, by means of a series of right-angled receding steps, seems to found a just claim for the Grand Gallery to be considered, in Mr. Proctor's words, "the finest pre-telescopic transit in- strument ever made." Had the walls of this great instrument slanted, the slightest movement on the part of an observer in either lowering or raising the level of his eyes would change the position of the points at which the star in transit out the slant. The sides being vertical, such movement would not affect the moment of appearance or disappearance in the slightest.
In "Studies of the Earth's Shape," the various observations and proofs of the earth's rotundity are pointed out and dis- cussed with that directness and simplicity which enabled Mr. Proctor to impress physical truths upon his hearers and readers. He tells us that one day, when travelling over the prairie region of Kansas, the illustration of the curvature of the earth's surface furnished by the rails stretching to the horizon—he being on the rear-platform of the train—struck him for the first time, and he never felt the rotundity of the earth so forcibly before. As he raised and lowered his body alternately, keeping his eyes fixed on the horizon, the ends alternately approached and drew apart, for the higher above the ground his eyes were, the further he could see, and the nearer more distant objects—in this case the ends of the rails— seemed to each other. But an even more striking illustra- tion of the rotundity of, say, water-surface, is that furnished by the telescope. An observer bringing into focus the rigging of a ship hull-down, can hardly ignore the fact that part of the surface of the sea is in the direct line between him and the hull. The sea-horizon itself is obviously not in.
focus, but by shortening the focus it. becomes clearly defined, while the rigging of the ship becomes indistinct; and if the change be made from one to the other continuously, "the observer," says Mr. Proctor, "seems to feel that the sea-sur- face rises in a bold sweep between him and the more distant object."
The chapter Ga the "Motions of the Sun, Moon, and Planets" is a most interesting summary of the history of astronomy and astrology ; and, "The True Mechanism of the Solar System" and the succeeding chapter, in which are col- lected the experiments made from time to time to determine distances, diurnal motion, the density of the earth, tides, and the many laws affecting our planet, contain some of the most instructive and well-expressed pages in the whole volume. The transit of Venus was a subject about which, some will remember, that a great discussion raged. Mr. Proctor came into collision with official astronomy, and carried the day on the point of having proper observations made. In his dis- course on the Inferior Planets, the Zone of Asteroids is treated with that aptness of illustration so peculiarly his own. We have ceased to be startled by the discovery of asteroids ; but the discovery of Ceres was a momentous event, and of a kind the "most surprising, rightly understood," made since Huyghens discovered the nature of the rings of Saturn. The gap between Mars and Jupiter, though leas than the distance between Jupiter and his next outer neighbour, Saturn, was unaccountable, there being an empirical law of increase in the distances between each planetary orbit and its next outer neighbour. In Kepler's time it was felt that a planet had disappeared,—probably blown to atoms, said some, on account of man's wickedness. Piazzi, on the first night of the nineteenth century, discovered what was supposed to be the missing planet. As in other in- stances, it was quite accidental, for Piazzi was not a member of the "Missing-World Detection Society," twenty-four in num- ber, who portioned out the zodiac amongst themselves for the search of the suspected planet. Ceres, however, had an orbit inclined to the plane of the ecliptic by as much as ten degrees, an unheard-of thing for the path of a planet, as any text- book of astronomy tells us that the planets lie nearly in one plane. The second asteroid, Pallas, was discovered to be three times as much inclined to the plane as Ceres, and the theory of an exploded planet seemed convincing. "Suppose," says Mr. Proctor, "our earth to explode on or about March 20th at noon ;" and he proceeds to detail the event. South Africa would be driven forwards, our Indian Empire backwards, along the path of the earth, and would still follow the same orbit; whereas the Polar Regions would travel on paths most inclined to the earth's former orbit, being propelled at right angles to the earth's motion. Olbers' theory, striking as it seemed at the time, is now known to be hopeless; and even Mr. Proctor can give no more decisive explanation of the asteroidal ring than to say :—" The Zone of Asteroids appears to represent a portion of the solar system, which, under more favourable conditions, would have developed into a single planet, but, disturbed by the attraction of the great planet Jupiter, remained scattered in the form of a widely strewn ring." This is unsatisfying; and though Mr. Proctor rightly deprecates the time spent on hunting for new asteroids, the Zone of Asteroids is obviously an unexplored region, and conceals some secret from us.
A great deal of romance has surrounded that part of pro- gressive astronomy which was signalised by the discovery of Neptune. Mr. Proctor, in his usual direct fashion, gives us a capital summary of the whole case, leaving nothing untouched or ignored. The existence of Neptune was, of course, a great triumph for the verification of Newton's law of gravity, perhaps the greatest triumph that a philosopher ever had, but the existence of the planet was not the complete surprise many have imagined it. The old saying about coming events was never more true. Though it is hardly just to judge the failure of those who failed to discover Neptune from the later standpoint of success, yet that he eluded detection so long seems a strange perversity. One man, acting on Adam's calculations, actually saw the planet twice, but failed to recognise its planetary character.
"The Stars" would have been the especial delight of Mr. Proctor; it is a sad loss, indeed, that be could not live to finish his great work. After the sentiments which he expresses in his preface as to the true dignity of astronomy, we may be sure the "Universe of Stars," would have been not only the last but the beet work of Mr. Proctor. The
editor has made the chapter as complete as possible, but it is, naturally, defective, though a profoundly interesting and suggestive account, and one that is wonderfully impressive with its many striking facts and almost inconceivable dis- tances. The diameter of the Milky Way, for instance, it is said, cannot be less than twenty times our distance from the nearest fixed star. Very little notice is taken of the spectra of the stare, the study of which has received such illustration from Huggins, Young, and Lockyer ; and Mr. C. Ranyard doubts the simple formula, "the hotter the star, the simpler the spectrum." He gives us a striking argument, by-the-way, for the extreme tenuity of the Orion Nebuhe. We must here regretfully take leave of Old and New Astronomy. It has one fault, a tendency to personalities ; but this the reader must forget.
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