lost sight of it. That it was really present all the time, however, though faint, is proved by the observations of Professor Eastman, Professor Brackett, Mr. Thomas and the writer, the former of whom traced it all around the sun to a distance of from 10' to 20', going twice over the ground, and keeping it in sight all the time. With the hydrogen lines the case was similar; the writer had one or other of them in the field continually, and they never quite disappeared, though at times very faint.

Of course, the slitless spectroscopes, both ocular and photographic, from which so much had been expected, failed to give any satisfactory results. In 1871, when the instruments were first used, the observers saw a series of colored images of the corona. Mr. Lockyer, for instance, saw four such images, one red, one green, one blue, and one violet. This year nothing of the kind appeared. At the moment, indeed, when totality began there was an exquisite exhibition, first of the darkness of the solar spectrum, and then for an instant of a multitude of bright colored segments -the spectrum of the chromosphere; but when the moon had covered the chromosphere there was only a disappointing, continuous band of color, unmarked by rings of any kind.

Those, also, who were looking for new bright lines in the corona spectrum were equally unsuccessful, whether they employed the ordinary spectroscope or worked by photography. Some of the observers, the writer among others, used a so-called "fluorescent eye-piece," which brings the otherwise invisible light beyond the extreme violet-end of the spectrum within the range of human eyes, by the action of a film of fluorescent liquid (æsculin solution) inclosed between thin plates of glass. But, although before totality the apparatus worked perfectly, disclosing to the eyes dark lines innumerable in the portion of the spectrum invisible without its aid, after the darkness came on it failed to show a single bright line. The most carefully prepared and sensitive photographic apparatus succeeded no better, except that Dr. Draper, Mr. Lockyer, and one or two others perhaps, did obtain by means of a slitless spectroscope, an impression of a faint continuous spectrum in the ultra violet, without rings or markings of any kind. Evidently no lines existed to see or photograph on this occasion.

One or two observations were made of some interest in their relation to previous work. Professor Rockwood, of the Princeton party, using a double-barreled slitless spectroscope, observed at the beginning of totality a bright red line in the chromosphere spectrum very near to B. This explains an observation of Mr. Pogson, in 1868, who then insisted that he saw B reversed in the spectrum of a prominence, but as all the other observers had C instead of B, his record was generally regarded as a mistake.

The line is probably one well known to solar spectroscopists, at 534 of Kirchhoff's scale-a line exceedingly difficult to see in the spectrum of the chromosphere under ordinary circumstances, but still invariably present and exhibitable (if one may coin a word) with proper appliances. Its conspicuousness in Professor Rockwood's instrument is a matter of some surprise, but there could be

no mistake, as C was even more brilliantly conspicuous at the same time. What the substance which causes it may be is quite unknown. Like the so-called D, line it has no corresponding dark line in the solar spectrum.

The same observer, and the writer also, saw both H lines (calcium) brightly reversed in the spectrum of the chromosphere; thus confirming observations made six years ago at Sherman, but never corroborated since, except by the photographic spectrum obtained by the Siam expedition in 1875.

The exquisite reversal of the dark Fraunhofer lines at the moment of totality was seen by many of the observers. Several observers, especially Professors Barker and Morton, at Rawlins, were able to confirm Janssen's observation in 1871 by seeing the principal dark Fraunhofer lines in the corona spectrum, thus showing that a considerable percentage of the coronal radiance is mere reflected sunlight. The dark lines were, however, so faint as to be seen by very few, and this shows equally clearly, we think, that the particles which reflected the sunlight are themselves also self-luminous, as, of course, they ought to be so near the sun.

A great deal of attention has been paid to the polarization of the coronal light in past eclipses, and while on the whole there has been an overwhelming weight of evidence in favor of radial polarization, yet at every eclipse some observer of reputation has obtained anomalous results quite at variance with all the others. This year Dr. Hastings of Baltimore, comes out with strong tangential polarization as his result. That he must be the victim of some mistake is almost certain, since all the rest of the observersWright, Ranyard, Harknesss and others—are emphatic and clear in their contrary conclusion.

Experiments with the tasimeter or new heat measure of Mr. Edison showed, as was ascertained many years ago, that the heat of the corona is quite sensible. With a thermopile attached to a peculiarly-arranged spectroscope Mr. Anderson, of the Princeton party, obtained a doubtful result, which may indicate a bright heat-line in that part of the chromosphere spectrum below the red.

It has been represented in some quarters that the results of this eclipse require a fundamental reconstruction of the theories hitherto held regarding the constitution of the corona. This is, however, an entire misapprehension. The same constituents appear in the corona as hitherto, only in altered proportions, as might have been and was expected by students of solar physics. In 1869, 1870 and 1871 the gaseous elements of the corona-the hydrogen and "1474 stuff," whatever that may be-were in such quantity and condition and rose so high above the solar surface that their lines were conspicuous in the coronal spectrum, and attracted the attention of observers far more forcibly than the feeble continuous spectrum of the light emitted from and reflected by, the minute solid or liquid particles which also constitute an essential element of the corona. At present the condition is reversed. The gases are either too small in quantity or too cool to be conspicuous. The lesson, and it is an important one, is simply,

as has been said, that, to a certain extent, the corona sympathizes with the sun-spots.

It certainly looks probable, also, that while the gaseous elements of the corona are strictly solar, the non-gaseous matter-the coronal dust or haze-is of extraneous and very likely meteoric origin. At any rate, the extent of the corona was certainly not less than on former occasions, whatever may have been the case with its brightness. In fact, it has never been traced quite so far from the sun before, as this time by Langley and Newcomb, who followed it out for six degrees along the ecliptic, a success partly, of course, due to the clearness of the air at their elevated stations. Now, this is quite consistent with the theory that meteor streams furnish the hazy matter of the coronal envelope, since, so far as we can judge, they have nothing to do with the sun-spots.

A very interesting problem relates to the effect of solar forces upon this meteoric matter, if such it really be, and the material for the study is furnished in rich abundance by the numerous drawings made by Langley, Abbe, Penrose, Boss and others, and by the photographs, which in excellence and number excel those obtained on any previous occasion. Among the best which we have seen are the magnificent series made by Rogers at La Junta, those of Draper at Rawlins, and those of the Princeton party at Denver; undoubtedly there are others of at least equal excellence.

To sum up: The eclipse of 1878 has added a new planet to the system, and has demonstrated that the unknown cause, whatever it may be, which produces the periodical sun spots at intervals of about eleven years, also affects the coronal atmosphere of the

sun.

This, of course, adds a certain measure of probability to the idea that these solar periods may produce some effect upon the earth, such as may be felt in our meteorological conditions; and though the writer by no means concurs with Mr. Lockyer in considering that Meldrum's investigations upon Indian cyclones have already demonstrated connection between the sun spots and the weather, but, on the other hand, thinks the connection almost disproved by results of other investigators, still there can be no question that the subject deserves thorough study.

The result of the late eclipse goes to show such a periodical change in the state of the solar atmosphere as might very possibly produce a sensible effect upon the earth; whether it does or not is a question which can be settled only by a careful and systematic investigation of the facts.

Princeton, N. J., Thursday, Aug. 15, 1878.

15. Institute of France.-Dr. Asa Gray has been elected Corresponding Member of the Institute in place of Alexander Braun, of Berlin, recently deceased.

Charles Darwin has also been made a Corresponding Member of the Institute.

16. The Annual Meeting of German Naturalists and Physicists will be held during the week from September 11-18, instead of the following week.

THE

AMERICAN

JOURNAL OF SCIENCE AND ARTS.

[THIRD SERIES.]

ART. XXVII.—On the Morphological Laws of the Configurations formed by Magnets floating vertically and subjected to the attraction of a superposed magnet; with notes on some of the phenomena in molecular structure which these experiments may serve to explain and illustrate; by ALFRED M. MAYER.

In the April and June numbers of this Journal (pages 276 and 477 of vol. xv), I published short notes on my experiments with magnets floating vertically and subjected to the attraction of a superposed magnet. The object of this paper is to present accurate diagrams of the configurations formed by the floating magnets and to give the laws ruling these configurations, with some notices of the peculiarities of these forms. At the same time I will show how neatly these experiments illustrate several phenomena in the molecular structure of matter.

The Diagrams.* - These diagrams show the configurations formed by numbers of magnets extending from two to twenty. They were obtained as follows: the number of needles forming a configuration were floated in a bowl filled to its brim with water. The eye ends of the needles, which protruded a short distance beyond the tops of the corks, were of S. polarity. A cylindrical magnet, 38cm long and 15mm in diameter, was clamped in a vertical position, with its N. end at the constant distance of 60 millimeters above the tip of the needle which floated in the line of the axis of the magnet. I tipped the ends of the needles with printer's ink, and when the configuration had formed and was stationary, I brought down upon the needles a piece of flat card-board, and thus obtained prints * I am indebted to the courtesy of Mr. A. E. Beach, of the Scientific American, for the use of the engravings of the diagrams which illustrate this article. AM. JOUR. SCI.-THIRD SERIES, VOL. XVI, No. 94.-Oct., 1878.