Science

THE theory of natural selection by no means affords the only instance in which the advance of science has been opposed on sentimental grounds. When Galileo, Scheiner, and Fabricius discovered the spots on the sun, the Aristotelians indignantly insisted that the thing was impossible ; the appearances must be due to defects in the lens of the telescope or in the eye of the observer. For, said they, it is incompatible with the dignity of the Eye of the Universe that it should be afflicted with vulgar ophthalmia!

Nevertheless, the spots are there, and this “solar ophthalmia” is turning out to be a fact of some consequence in its bearings upon the mutual relations of the members of the solar system, to say nothing of the significance which it may have with reference to the constitution of the sun itself. In 1826 Schwabe began a series of observations which, for patient accuracy and persevering thoroughness, have rarely been matched in the history of astronomy. During more than forty years Schwabe has watched the sun on every day on which it has been visible, counting, describing, and tabulating the spots. The result at which he arrived after a dozen years, and which after another dozen years began to be generally accepted by astronomers, was the discovery of a marked periodicity in the numbers of the spots. During a period of rather more than eleven years, the spots increase steadily, though not quite uniformly in number, until they have attained a maximum at about the middle of the period, after which they steadily decrease to a minimum. But now a remarkable parallelism to this periodicity was observed in the case of certain terrestrial phenomena. The magnetized compass-needle oscillates daily upon its pivot with great uniformity, “the oscillation corresponding to a very slight tendency on the part of that end of the needle which lies nearest to the sun to direct itself towards his place.” But every now and then there are sudden disturbances in the regularity of this motion, indicating that a magnetic storm is taking place over a considerable part of the earth’s surface. These disturbances of the magnetic needle regularly increase and diminish in frequency through periods corresponding with the periods of maximum and minimum frequency of the solar spots. When the spots are most numerous, the magnetic disturbance is greatest; when the spots are least numerous, the magnetic disturbance is at its minimum; and in the various degrees between maximum and minimum there is a similar close correspondence. To complete the parallelism, a sudden or extraordinary outbreak of solar spots is accompanied by sudden and unusual magnetic disturbance on the earth. For example, on September 1, 1859, the appearance of two great spots which travelled over the solar surface at the rate of seven thousand miles per minute was immediately followed by the greatest magnetic storm on record. Auroras of extraordinary brilliancy were seen in all parts of the earth, Compass-needles were turned quite out of place, and telegraph-wires sent forth severe electric shocks, and in one or two cases set fire to the apparatus attached to them.

From numberless such correspondences it is concluded that some causal connection exists between the phenomena of terrestrial magnetism and the atmospheric disturbances on the sun of which the spots are the indication. Without entering upon the various theories which have been propounded concerning the physical character of the solar spots, we may observe that it is conceded on all hands that they are appearances due to violent tornadoes or cyclones in the gaseous matter surrounding the sun. In view of this admitted fact it becomes interesting to note that there is a second curious parallelism between the behavior of sun-spots and the positions of sundry planets, —notably of Mercury, Venus, the Earth, Jupiter, and Saturn. Several years ago Professor Wolf observed that, superposed upon the well-marked periods of eleven years, there are minor periods of variation in the spots. These secondary maxima and minima succeed each other at intervals of 7.65 months, or 0.637 of one year, an interval which almost exactly corresponds with the annual period of Venus. But recent careful investigations, conducted by Messrs. Balfour Stewart, De la. Rue, and Loewy, have elicited the fact that the average size of a spot is greatest on the side of the sun which is turned away from Venus or Mercury, and smallest on the side nearest one of these planets. And further, as any spot traverses the central longitude of the disk, its average area is greatest when Venus and the Earth are 180 degrees apart, and least when the two planets are together; and the same order is preserved when Mercury and Jupiter are taken into the account. Mr. Carrington has moreover shown that spots increase in frequency as Jupiter recedes from the sun ; and, lastly, M, Wolf has detected a longer period of fifty-six years of spot-variation, in which the maximum answers to the epoch at which the aphelion of Jupiter coincides with that of Saturn.

Putting together these various conclusions, it seems clear that those planets which, either from size or from proximity, exert the greatest gravitative force upon the sun, also affect in a marked degree the phenomena of spots. That no effects have as yet been attributable to the small and distant Mars, or to the large but enormously distant Uranus and Neptune, is a signficant item of evidence in favor of the view that it is through simple gravitation, and not through any more mysterious kind of influence, that the other planets produce their notable effects upon the sun’s surface. The conclusion seems plainly brought before us, that the variations of the spots are due to tidal movements of the solar atmosphere, caused by planetary gravitation.

An admirable scientific work for popular perusal is Dr. Schellen’s " Spectrum Analysis,” ¹ though, when we say " popular perusal,” we do not mean to imply that the book can be comfortably or intelligently read by persons ignorant of the rudiments of chemistry, physics, and astronomy. That there is no royal road to the understanding of a subject like spectrum analysis, however simple and beautiful the principle on which it depends, must appear to every one moderately acquainted with physical science. In Dr. Schellen’s work the subject gets the fullest and most lucid treatment which it has yet received at the hands of any one, and it is thus the best exposition for general reading, though its intrinsic superiority to the excellent treatise of Professor Roscoe is probably no greater than is due to its more recent date and the increased number of observations contained in it.

The names of Professors Huxley, Roscoe, and Balfour Stewart are a sufficient guaranty of the excellence of the series of " Science Primers ” which are edited by these gentlemen and published by D. Appleton & Co. We have received two of the series, — the “ Chemistry ” by Roscoe, and the " Physics ” by Balfour Stewart. They are little volumes, containing each from one hundred to one hundred and twenty-five pages ; yet the amount of matter got into this small space is somewhat surprising. In the " Physics,” for example, we get not only a general account of gravity, cohesion, and chemism, of the three states of matter, of the properties of solids, liquids, and gases, but also an admirably clear exposition of the principles of energy, of bodies in motion and in undulation, of sound, light, heat, and electricity, and of the transformation of motion. It is to be hoped that the series will be continued. The willingness of such eminent inquirers to write popular books on science, to take the place of the wretched trash with which we were till lately obliged to content ourselves, is one of the most encouraging signs of the times.

“ The Popular Science Monthly,” conducted by E. L. Youmans and published by D. Appleton & Co., meets a real popular want, and, if one may judge from the opening number, it is likely to be highly satisfactory. The articles, indeed, are chiefly by English writers, but that is, in a measure, a necessity which time will do away with. The satisfactory point is that the articles are all good ; the weakest one in the number being probably that of M. de Quatrefages, with its antiquated Cuvierian views of species. The leading article, on “ The Study of Sociology,” is by Herbert Spencer, and it is needless to say that it is both sensible and profound; but it may be well enough to remark that it is very easy and entertaining reading, being designedly written in a popular style. Unlike many epoch-making philosophers, Mr. Spencer’s power of lucid exposition fully equals his power of original thinking ; and difficult as his more elaborate works are, by reason of the very profundity of the inquiry, no one knows better how to be easy and entertaining when occasion is offered. The publication of this article is an earnest of the progress which Mr. Spencer is making in his colossal work. That work is about half finished, the division on psychology wanting but one or two more numbers, while the division on sociology will doubtless soon begin to appear. As a sort of byplay while engaged upon his greater work, Mr. Spencer writes this series of ten or a dozen articles on sociology, which are to appear in Dr. Youmans’s journal and will form one of its most attractive features.

Having spoken of popular scientific books which are good, we may for contrast call attention to one which is bad. “The World before the Deluge,” ² is one of the many sensational romances which M. Louis Figuier has seen fit to publish under the guise of science. Not that there is no science in the book, or that what science is found there is not sometimes well presented. No doubt there is much which to many readers would be instructive as well as agreeable. But M. Figuier is a thoroughly careless, untrained, and untrustworthy writer. Of scientific method, and of the exigencies of scientific proof, he has no more conception than a young-lady novelist; and he possesses very little of that useful common sense which sometimes renders good service in lieu of rigorous scientific training. Along with an extensive smattering of other men’s scientific knowledge, M. Figuier combines more or less of original vagary, and the result is such a book as the one before us, the very title of which is, in the present state of geology, an amusing anachronism.

“ How the World was peopled” is the title of a book by the Rev. Edward Fontaine, in which it is maintained that all existing races are the descendants of Adam and Eve. We have not had time to examine this book thoroughly, but we hope the following is not a fair specimen of its accuracy : “ The absurdity of the idea that the progenitors of men were monkeys, or inferior mammalia of some sort, has been exposed sufficiently by Lyell, Agassiz, Mivart, and other naturalists. They have thought the subject worthy of a serious scientific discussion. I therefore (!) mention it,” etc., etc. Now since Lyell and Mivart both accept the idea that “the progenitors of men were monkeys,” we cannot but think that Mr. Fontaine has too carelessly studied a subject which cannot safely be slighted in treating the question, how the world was peopled. For the benefit of those whose ideas on this point may perhaps partake of the cloudiness of Mr. Fontaine’s, we may as well indicate the source of the error. Before 1859 Lyell opposed the development theory of man’s origin, as did the majority of naturalists; but after the publication of Mr. Darwin’s researches, Lyell changed his opinion, as did the majority of naturalists, and in 1863 he declared himself a Darwinian. Probably Mr. Fontaine has consulted only some old edition of Lyell’s “Geology”; but that is a very dangerous thing to do when one is writing about scientific matters. As for Mr. Mivart, he is not a Darwinian ; that is, he does not accept the theory of the origin of species by means of natural selection ; nevertheless, he is very careful to inform his readers that he does accept the development theory, that is, he does believe that the human organism is physically derived from the organism of an ancient ape. It should be better understood than it seems to be, that the essentially Darwinian part of “ Darwinism” is not the theory that man has been evolved from a lower form of mammalian life. Whether true or not, this theory was held by a large proportion of the ablest naturalists during the fifty years preceding the publication of Mr. Darwin’s views. What Mr. Darwin did was not to originate the theory, but to give it a scientific character by means of his discovery of natural selection. What Mr. Mivart has done has been to adopt the theory, while seeking to deprive it of its scientific character by rejecting or subordinating the agency of natural selection, and leaving open as large a field as possible for the play of mythologic fancies. It is quite possible, therefore, for a writer to attack Mr. Darwin and still to hold that his grandfather was a monkey ; and this, doubtless, did not occur to Mr. Fontaine.

We ought not to conclude without a reference to the republication, by D. Appleton & Co., of Sir John Lubbock’s standard treatise on “ Pre-historic Times.” The excellence of the work is so well known that any praise we could give it would be superfluous.